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  • 1.
    Andersson, L.
    et al.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    Ergun, R. E.
    Univ Colorado, LASP, Boulder, CO 80309 USA.;Univ Colorado, APS, Boulder, CO 80309 USA..
    Delory, G. T.
    Univ Calif Berkeley, SSL, Berkeley, CA 94720 USA..
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Westfall, J.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    Reed, H.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    McCauly, J.
    Univ Calif Berkeley, SSL, Berkeley, CA 94720 USA..
    Summers, D.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    Meyers, D.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    The Langmuir Probe and Waves (LPW) Instrument for MAVEN2015Ingår i: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 195, nr 1-4, s. 173-198Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    We describe the sensors, the sensor biasing and control, the signal-processing unit, and the operation of the Langmuir Probe and Waves (LPW) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. The LPW instrument is designed to measure the electron density and temperature in the ionosphere of Mars and to measure spectral power density of waves (DC-2 MHz) in Mars' ionosphere, including one component of the electric field. Low-frequency plasma waves can heat ions resulting in atmospheric loss. Higher-frequency waves are used to calibrate the density measurement and to study strong plasma processes. The LPW is part of the Particle and Fields (PF) suite on the MAVEN spacecraft. The LPW instrument utilizes two, 40 cm long by 0.635 cm diameter cylindrical sensors with preamplifiers, which can be configured to measure either plasma currents or plasma waves. The sensors are mounted on a pair of meter long stacer booms. The sensors and nearby surfaces are controlled by a Boom Electronics Board (BEB). The Digital Fields Board (DFB) conditions the analog signals, converts the analog signals to digital, processes the digital signals including spectral analysis, and packetizes the data for transmission. The BEB and DFB are located inside of the Particle and Fields Digital Processing Unit (PFDPU).

  • 2.
    Andersson, L.
    et al.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Weber, T. D.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Malaspina, D.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Crary, F.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Ergun, R. E.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Delory, G. T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Fowler, C. M.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Morooka, M. W.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    McEnulty, T.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Eriksson, Anders. I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Andrews, David. J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Horanyi, M.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Collette, A.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Yelle, R.
    Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA..
    Jakosky, B. M.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Dust observations at orbital altitudes surrounding Mars2015Ingår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 350, nr 6261, artikel-id aad0398Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dust is common close to the martian surface, but no known process can lift appreciable concentrations of particles to altitudes above similar to 150 kilometers. We present observations of dust at altitudes ranging from 150 to above 1000 kilometers by the Langmuir Probe and Wave instrument on the Mars Atmosphere and Volatile Evolution spacecraft. Based on its distribution, we interpret this dust to be interplanetary in origin. A comparison with laboratory measurements indicates that the dust grain size ranges from 1 to 12 micrometers, assuming a typical grain velocity of similar to 18 kilometers per second. These direct observations of dust entering the martian atmosphere improve our understanding of the sources, sinks, and transport of interplanetary dust throughout the inner solar system and the associated impacts on Mars's atmosphere.

  • 3.
    Andrews, David
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Edberg, Niklas J. T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Gurnett, D. A.
    Morgan, D.
    Nemec, F.
    Opgenoorth, Hermann J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Control of the topside Martian ionosphere by crustal magnetic fields2015Ingår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, nr 4, s. 3042-3058Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present observations from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument onboard Mars Express of the thermal electron plasma density of the Martian ionosphere and investigate the extent to which it is influenced by the presence of Mars's remnant crustal magnetic fields. We use locally measured electron densities, derived when MARSIS is operating in active ionospheric sounding (AIS) mode, covering an altitude range from approximate to 300km to approximate to 1200km. We compare these measured densities to an empirical model of the dayside ionospheric plasma density in this diffusive transport-dominated regime. We show that small spatial-scale departures from the averaged values are strongly correlated with the pattern of the crustal fields. Persistently elevated densities are seen in regions of relatively stronger crustal fields across the whole altitude range. Comparing these results with measurements of the (scalar) magnetic field also obtained by MARSIS/AIS, we characterize the dayside strength of the draped magnetic fields in the same regions. Finally, we provide a revised empirical model of the plasma density in the Martian ionosphere, including parameterizations for both the crustal field-dominated and draping-dominated regimes.

  • 4.
    Andrews, David J.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Andersson, L.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    Delory, G. T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Ergun, R. E.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Fowler, C. M.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    McEnulty, T.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    Morooka, M. W.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    Weber, T.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    Jakosky, B. M.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    Ionospheric plasma density variations observed at Mars by MAVEN/LPW2015Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, nr 21, s. 8862-8869Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on initial observations made by the Langmuir Probe and Waves relaxation sounding experiment on board the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. These measurements yield the ionospheric thermal plasma density, and we use these data here for an initial survey of its variability. Studying orbit-to-orbit variations, we show that the relative variability of the ionospheric plasma density is lowest at low altitudes near the photochemical peak, steadily increases toward higher altitudes and sharply increases as the spacecraft crosses the terminator and moves into the nightside. Finally, despite the small volume of data currently available, we show that a clear signature of the influence of crustal magnetic fields on the thermal plasma density fluctuations is visible. Such results are consistent with previously reported remote measurements made at higher altitudes, but crucially, here we sample a new span of altitudes between similar to 130 and similar to 300 km using in situ techniques.

  • 5.
    André, Mats
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Li, K.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Outflow of low-energy ions and the solar cycle2015Ingår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, nr 2, s. 1072-1085Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Magnetospheric ions with energies less than tens of eV originate from the ionosphere. Positive low-energy ions are complicated to detect onboard sunlit spacecraft at higher altitudes, which often become positively charged to several tens of volts. We use two Cluster spacecraft and study low-energy ions with a technique based on the detection of the wake behind a charged spacecraft in a supersonic ion flow. We find that low-energy ions usually dominate the density and the outward flux in the geomagnetic tail lobes during all parts of the solar cycle. The global outflow is of the order of 10(26) ions/s and often dominates over the outflow at higher energies. The outflow increases by a factor of 2 with increasing solar EUV flux during a solar cycle. This increase is mainly due to the increased density of the outflowing population, while the outflow velocity does not vary much. Thus, the outflow is limited by the available density in the ionospheric source rather than by the energy available in the magnetosphere to increase the velocity.

  • 6.
    André, Mats
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Rymd- och plasmafysik.
    Graham, Daniel B.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Karlsson, T.
    KTH Royal Inst Technol, Sch Elect Engn, Dept Space & Plasma Phys, Stockholm, Sweden.
    Wieser, G. Stenberg
    Swedish Inst Space Phys, Kiruna, Sweden.
    Vigren, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Norgren, Cecilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Rymd- och plasmafysik.
    Johansson, Fredrik L.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Henri, P.
    Lab Phys & Chim Environm & Espace, Orleans, France.
    Rubin, M.
    Univ Bern, Phys Inst, Bern, Switzerland.
    Richter, I.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Braunschweig, Germany.
    Lower hybrid waves at comet 67P/Churyumov-Gerasimenko2017Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, s. S29-S38Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the generation of waves in the lower hybrid frequency range by density gradients in the near plasma environment of comet 67P/Churyumov-Gerasimenko. When the plasma is dominated by water ions from the comet, a situation with magnetized electrons and unmagnetized ions is favourable for the generation of lower hybrid waves. These waves can transfer energy between ions and electrons and reshape the plasma environment of the comet. We consider cometocentric distances out to a few hundred km. We find that when the electron motion is not significantly interrupted by collisions with neutrals, large average gradients within tens of km of the comet, as well as often observed local large density gradients at larger distances, are often likely to be favourable for the generation of lower hybrid waves. Overall, we find that waves in the lower hybrid frequency range are likely to be common in the near plasma environment.

  • 7.
    Broiles, Thomas W.
    et al.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Burch, J. L.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Chae, K.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Clark, G.
    Johns Hopkins Univ, Appl Phys Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA..
    Cravens, T. E.
    Univ Kansas, Dept Phys & Astron, 1450 Jayhawk Blvd, Lawrence, KS 66045 USA..
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Fuselier, S. A.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Frahm, R. A.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Gasc, S.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Goldstein, R.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Henri, P.
    CNRS, LPC2E, F-45071 Orleans, France..
    Koenders, C.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Livadiotis, G.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Mandt, K. E.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Mokashi, P.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Nemeth, Z.
    Wigner Res Ctr Phys, H-1121 Budapest, Hungary..
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Rymd- och plasmafysik. Univ Kansas, Dept Phys & Astron, 1450 Jayhawk Blvd, Lawrence, KS 66045 USA..
    Rubin, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Samara, M.
    Goddard Space Flight Ctr, Heliophys Div, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA..
    Statistical analysis of suprathermal electron drivers at 67P/Churyumov-Gerasimenko2016Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, s. S312-S322Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We use observations from the Ion and Electron Sensor (IES) on board the Rosetta spacecraft to study the relationship between the cometary suprathermal electrons and the drivers that affect their density and temperature. We fit the IES electron observations with the summation of two kappa distributions, which we characterize as a dense and warm population (similar to 10 cm(-3) and similar to 16 eV) and a rarefied and hot population (similar to 0.01 cm(-3) and similar to 43 eV). The parameters of our fitting technique determine the populations' density, temperature, and invariant kappa index. We focus our analysis on the warm population to determine its origin by comparing the density and temperature with the neutral density and magnetic field strength. We find that the warm electron population is actually two separate sub-populations: electron distributions with temperatures above 8.6 eV and electron distributions with temperatures below 8.6 eV. The two sub-populations have different relationships between their density and temperature. Moreover, the two sub-populations are affected by different drivers. The hotter sub-population temperature is strongly correlated with neutral density, while the cooler sub-population is unaffected by neutral density and is only weakly correlated with magnetic field strength. We suggest that the population with temperatures above 8.6 eV is being heated by lower hybrid waves driven by counterstreaming solar wind protons and newly formed, cometary ions created in localized, dense neutral streams. To the best of our knowledge, this represents the first observations of cometary electrons heated through wave-particle interactions.

  • 8.
    Buchert, Stephan C.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Gill, Reine
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Nilsson, Thomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Åhlén, Lennart
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Wahlund, Jan-Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Knudsen, David
    Univ Calgary, Calgary, AB, Canada..
    Burchill, Johnathan
    Univ Calgary, Calgary, AB, Canada..
    Archer, William
    Univ Calgary, Calgary, AB, Canada..
    Kouznetsov, Alexei
    Univ Calgary, Calgary, AB, Canada..
    Stricker, Nico
    ESA ESTEC, Noordwijk, Netherlands..
    Bouridah, Abderrazak
    ESA ESTEC, Noordwijk, Netherlands..
    Bock, Ralph
    ESA ESTEC, Noordwijk, Netherlands..
    Haggstrom, Ingemar
    EISCAT Sci Assoc, Headquarters, Kiruna, Sweden..
    Rietveld, Michael
    EISCAT Sci Assoc, Tromso, Norway..
    Gonzalez, Sixto
    Natl Astron & Ionosphere Ctr, Arecibo, PR USA..
    Aponte, Nestor
    Natl Astron & Ionosphere Ctr, Arecibo, PR USA..
    First results from the Langmuir probes on the Swarm satellites2014Ingår i: 2014 XXXITH URSI General Assembly And Scientific Symposium (URSI GASS), 2014Konferensbidrag (Refereegranskat)
  • 9.
    Buchert, Stephan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Zangerl, Franz
    Sust, Manfred
    André, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Wahlund, Jan-Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Opgenoorth, Hermann
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    SWARM observations of equatorial electron densities and topside GPS track losses2015Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, nr 7, s. 2088-2092Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The SWARM satellites have both upward looking GPS receivers and Langmuir probes. The receivers repeatedly lost track of the L1 band signal in January-February 2014 at postsunset hours, when SWARM was at nearly 500km altitude. This indicates that the signal was disturbed by ionospheric irregularities at this height and above. The track losses occurred right at density gradients associated with equatorial plasma bubbles and predominantly where the measured background density was highest. The signal showed strong phase scintillations rather than in amplitude, indicating that SWARM might be in the near field of an ionospheric phase screen. Density biteouts, depletions between steep gradients, were up to almost 3 orders of magnitude deep in the background of a more shallow trough centered at the magnetic equator. Comparison between satellites shows that the biteout structure strongly varied in longitude over approximate to 100km and has in north-south steep walls.

  • 10.
    Deca, Jan
    et al.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA.;NASA, SSERVI, Inst Modeling Plasma Atmospheres & Cosm Dus, Moffett Field, CA 94035 USA..
    Divin, Andrey
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen. St Petersburg State Univ, Phys Dept, St Petersburg 198504, Russia.
    Henri, Pierre
    CNRS, LPC2E, F-45071 Orleans, France..
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Markidis, Stefano
    KTH Royal Inst Technol, S-10044 Stockholm, Sweden..
    Olshevsky, Vyacheslav
    Katholieke Univ Leuven, Ctr Math Plasma Astrophys CmPA, B-3001 Leuven, Belgium..
    Horányi, Mihály
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA.;NASA, SSERVI, Inst Modeling Plasma Atmospheres & Cosm Dus, Moffett Field, CA 94035 USA..
    Electron and Ion Dynamics of the Solar Wind Interaction with a Weakly Outgassing Comet2017Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 118, nr 20, artikel-id 205101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using a 3D fully kinetic approach, we disentangle and explain the ion and electron dynamics of the solar wind interaction with a weakly outgassing comet. We show that, to first order, the dynamical interaction is representative of a four-fluid coupled system. We self-consistently simulate and identify the origin of the warm and suprathermal electron distributions observed by ESA's Rosetta mission to comet 67P/Churyumov-Gerasimenko and conclude that a detailed kinetic treatment of the electron dynamics is critical to fully capture the complex physics of mass-loading plasmas.

  • 11.
    Edberg, Niklas J. T.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Alho, M.
    Aalto Univ, Sch Elect Engn, Dept Radio Sci & Engn, POB 13000, FI-00076 Aalto, Finland..
    André, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Andrews, David J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Behar, E.
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden..
    Burch, J. L.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Carr, C. M.
    Imperial Coll London, Exhibit Rd, London SW7 2AZ, England..
    Cupido, E.
    Imperial Coll London, Exhibit Rd, London SW7 2AZ, England..
    Engelhardt, Ilka. A. D.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Glassmeier, K. -H
    Goetz, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Goldstein, R.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Henri, P.
    Lab Phys & Chim Environm & Espace, F-45071 Orleans 2, France..
    Johansson, Fredrik L.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Koenders, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Mandt, K.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Moestl, C.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria..
    Nilsson, H.
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden..
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Richter, I.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Wedlund, C. Simon
    Univ Oslo, Dept Phys, Box 1048 Blindern, N-0316 Oslo, Norway..
    Wieser, G. Stenberg
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden..
    Szego, K.
    Wigner Res Ctr Phys, Konkoly Thege Miklos Ut 29-33, H-1121 Budapest, Hungary..
    Vigren, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Volwerk, M.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria..
    CME impact on comet 67P/Churyumov-Gerasimenko2016Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, s. S45-S56Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present Rosetta observations from comet 67P/Churyumov-Gerasimenko during the impact of a coronal mass ejection (CME). The CME impacted on 2015 Oct 5-6, when Rosetta was about 800 km from the comet nucleus, and 1.4 au from the Sun. Upon impact, the plasma environment is compressed to the level that solar wind ions, not seen a few days earlier when at 1500 km, now reach Rosetta. In response to the compression, the flux of suprathermal electrons increases by a factor of 5-10 and the background magnetic field strength increases by a factor of similar to 2.5. The plasma density increases by a factor of 10 and reaches 600 cm(-3), due to increased particle impact ionization, charge exchange and the adiabatic compression of the plasma environment. We also observe unprecedentedly large magnetic field spikes at 800 km, reaching above 200 nT, which are interpreted as magnetic flux ropes. We suggest that these could possibly be formed by magnetic reconnection processes in the coma as the magnetic field across the CME changes polarity, or as a consequence of strong shears causing Kelvin-Helmholtz instabilities in the plasma flow. Due to the limited orbit of Rosetta, we are not able to observe if a tail disconnection occurs during the CME impact, which could be expected based on previous remote observations of other CME-comet interactions.

  • 12.
    Edberg, Niklas J. T.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Henri, P.
    Lebreton, J. -P
    Gasc, S.
    Rubin, M.
    André, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Gill, Reine
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Johansson, Erik P. G.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Johansson, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Vigren, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Wahlund, Jan-Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Carr, C. M.
    Cupido, E.
    Glassmeier, K. -H
    Goldstein, R.
    Koenders, C.
    Mandt, K.
    Nemeth, Z.
    Nilsson, H.
    Richter, I.
    Wieser, G. Stenberg
    Szego, K.
    Volwerk, M.
    Spatial distribution of low-energy plasma around comet 67P/CG from Rosetta measurements2015Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, nr 11, s. 4263-4269Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We use measurements from the Rosetta plasma consortium Langmuir probe and mutual impedance probe to study the spatial distribution of low-energy plasma in the near-nucleus coma of comet 67P/Churyumov-Gerasimenko. The spatial distribution is highly structured with the highest density in the summer hemisphere and above the region connecting the two main lobes of the comet, i.e., the neck region. There is a clear correlation with the neutral density and the plasma to neutral density ratio is found to be approximate to 1-210(-6), at a cometocentric distance of 10km and at 3.1AU from the Sun. A clear 6.2h modulation of the plasma is seen as the neck is exposed twice per rotation. The electron density of the collisionless plasma within 260km from the nucleus falls off with radial distance as approximate to 1/r. The spatial structure indicates that local ionization of neutral gas is the dominant source of low-energy plasma around the comet.

  • 13.
    Edberg, Niklas J. T.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Rymd- och plasmafysik.
    Vigren, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Andrews, D. J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Johansson, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Burch, J. L.
    SW Res Inst, San Antonio, TX USA..
    Carr, C. M.
    Univ London Imperial Coll Sci Technol & Med, Space & Atmospher Phys Grp, London, England..
    Cupido, E.
    Univ London Imperial Coll Sci Technol & Med, Space & Atmospher Phys Grp, London, England..
    Glassmeier, K. -H
    Goldstein, R.
    SW Res Inst, San Antonio, TX USA..
    Halekas, J. S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Henri, P.
    Lab Phys & Chim Environm & Espace, Orleans, France..
    Koenders, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Braunschweig, Germany..
    Mandt, K.
    SW Res Inst, San Antonio, TX USA..
    Mokashi, P.
    SW Res Inst, San Antonio, TX USA..
    Nemeth, Z.
    Wigner Res Ctr Phys, Budapest, Hungary..
    Nilsson, H.
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden..
    Ramstad, R.
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden..
    Richter, I.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Braunschweig, Germany..
    Wieser, G. Stenberg
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden..
    Solar wind interaction with comet 67P: Impacts of corotating interaction regions2016Ingår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, nr 2, s. 949-965Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present observations from the Rosetta Plasma Consortium of the effects of stormy solar wind on comet 67P/Churyumov-Gerasimenko. Four corotating interaction regions (CIRs), where the first event has possibly merged with a coronal mass ejection, are traced from Earth via Mars (using Mars Express and Mars Atmosphere and Volatile EvolutioN mission) to comet 67P from October to December 2014. When the comet is 3.1-2.7AU from the Sun and the neutral outgassing rate approximate to 10(25)-10(26)s(-1), the CIRs significantly influence the cometary plasma environment at altitudes down to 10-30km. The ionospheric low-energy (approximate to 5eV) plasma density increases significantly in all events, by a factor of >2 in events 1 and 2 but less in events 3 and 4. The spacecraft potential drops below -20V upon impact when the flux of electrons increases. The increased density is likely caused by compression of the plasma environment, increased particle impact ionization, and possibly charge exchange processes and acceleration of mass-loaded plasma back to the comet ionosphere. During all events, the fluxes of suprathermal (approximate to 10-100eV) electrons increase significantly, suggesting that the heating mechanism of these electrons is coupled to the solar wind energy input. At impact the magnetic field strength in the coma increases by a factor of 2-5 as more interplanetary magnetic field piles up around the comet. During two CIR impact events, we observe possible plasma boundaries forming, or moving past Rosetta, as the strong solar wind compresses the cometary plasma environment. We also discuss the possibility of seeing some signatures of the ionospheric response to tail disconnection events.

  • 14.
    Engelhardt, Ilka. A. D.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Rymd- och plasmafysik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Vigren, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Valliéres, X.
    Rubin, M.
    Gilet, N.
    Henri, P.
    Cold electrons at comet 67P/Churyumov-Gerasimenko2018Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, artikel-id A51Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. The electron temperature of the plasma is one important aspect of the environment. Electrons created by photoionization or impact ionization of atmospheric gas have energies ∼10 eV. In an active comet coma the gas density is high enough for rapid cooling of the electron gas to the neutral gas temperature (few hundred kelvin). How cooling evolves in less active comets has not been studied before.

    Aims. To investigate how electron cooling varied as comet 67P/Churyumov-Gerasimenko changed its activity by three orders of magnitude during the Rosetta mission.

    Methods. We use in-situ data from Rosetta plasma and neutral gas sensors. By combining Langmuir probe bias voltage sweeps and Mutual Impedance Probe measurements we determine when cold electrons form at least 25% of the total electron density. We compare the results to what is expected from simple models of electron cooling, using the observed neutral gas density as input.

    Results. We demonstrate that the slope of the Langmuir probe sweep can be used as a proxy for cold electron presence. We show statistics of cold electron observations over the 2 year mission period. We find cold electrons at lower activity than expected by a simple model based on free radial expansion and continuous loss of electron energy. Cold electrons are seen mainly when the gas density indicates an exobase may have formed.

    Conclusions. Collisional cooling of electrons following a radial outward path is not sufficient for explaining the observations. We suggest the ambipolar electric field is important for the observed cooling. This field keeps electrons in the inner coma for much longer time, giving them time to dissipate energy by collisions with the neutrals. We conclude there is need of better models to describe the plasma environment of comets, including at least two populations of electrons and the ambipolar field.

  • 15.
    Engelhardt, Ilka. A. D.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Rymd- och plasmafysik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Stenberg Wieser, G.
    Goetz, C.
    Rubin, M.
    Henri, P.
    Nilsson, H.
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Rymd- och plasmafysik.
    Hajra, R.
    Valliéres, X.
    Plasma Density Structures at Comet 67P/Churyumov-Gerasimenko2018Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 477, nr 1, s. 1296-1307Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present Rosetta RPC case study from four events at various radial distance, phase angle and local time from autumn 2015, just after perihelion of comet 67P/Churyumov-Gerasimenko. Pulse like (high amplitude, up to minutes in time) signatures are seen with several RPC instruments in the plasma density (LAP, MIP), ion energy and flux (ICA) as well as magnetic field intensity (MAG). Furthermore the cometocentric distance relative to the electron exobase is seen to be a good organizing parameter for the measured plasma variations. The closer Rosetta is to this boundary, the more pulses are measured. This is consistent with the pulses being filaments of plasma originating from the diamagnetic cavity boundary as predicted by simulations. 

  • 16.
    Engelhardt, Ilka. A. D.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Rymd- och plasmafysik.
    Wahlund, Jan -Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Andrews, David J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders. I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Ye, S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Kurth, W. S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Gurnett, D. A.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Morooka, M. W.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Farrell, W. M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Dougherty, M. K.
    Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2BZ, England..
    Plasma regions, charged dust and field-aligned currents near Enceladus2015Ingår i: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 117, s. 453-469Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We use data from several instruments on board Cassini to determine the characteristics of the plasma and dust regions around Saturn's moon Enceladus. For this we utilize the Langmuir probe and the electric antenna connected to the wideband receiver of the radio and plasma wave science (RPWS) instrument package as well as the magnetometer (MAG). We show that there are several distinct plasma and dust regions around Enceladus. Specifically they are the plume filled with neutral gas, plasma, and charged dust, with a distinct edge boundary region. Here we present observations of a new distinct plasma region, being a dust trail on the downstream side. This is seen both as a difference in ion and electron densities, indicating the presence of charged dust, and directly from the signals created on RPWS antennas by the dust impacts on the spacecraft. Furthermore, we show a very good scaling of these two independent dust density measurement methods over four orders of magnitude in dust density, thereby for the first time cross-validating them. To establish equilibrium with the surrounding plasma the dust becomes negatively charged by attracting free electrons. The dust distribution follows a simple power law and the smallest dust particles in the dust trail region are found to be 10 nm in size as well as in the edge region around the plume. Inside the plume the presence of even smaller particles of about 1 nm is inferred. From the magnetic field measurements we infer strong field-aligned currents at the geometrical edge of Enceladus.

  • 17.
    Engwall, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Cully, Christopher M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    André, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Puhl-Quinn, Pamela
    Space Science Center, University of New Hampshire, Durham, New Hampshire 03824-3525, USA.
    Vaith, Hans
    Space Science Center, University of New Hampshire, Durham, New Hampshire 03824-3525, USA.
    Torbert, Roy
    Space Science Center, University of New Hampshire, Durham, New Hampshire 03824-3525, USA.
    Survey of cold ionospheric outflows in the magnetotail2009Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 27, nr 8, s. 3185-3201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low-energy ions escape from the ionosphere and constitute a large part of the magnetospheric content, especially in the geomagnetic tail lobes. However, they are normally invisible to spacecraft measurements, since the potential of a sunlit spacecraft in a tenuous plasma in many cases exceeds the energy-per-charge of the ions, and little is therefore known about their outflow properties far from the Earth. Here we present an extensive statistical study of cold ion outflows (0-60 eV) in the geomagnetic tail at geocentric distances from 5 to 19 R-E using the Cluster spacecraft during the period from 2001 to 2005. Our results were obtained by a new method, relying on the detection of a wake behind the spacecraft. We show that the cold ions dominate in both flux and density in large regions of the magnetosphere. Most of the cold ions are found to escape from the Earth, which improves previous estimates of the global outflow. The local outflow in the magnetotail corresponds to a global outflow of the order of 10(26) ions s(-1). The size of the outflow depends on different solar and magnetic activity levels.

  • 18.
    Ergun, R. E.
    et al.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Andersson, L. A.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Fowler, C. M.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Woodson, A. K.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Weber, T. D.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Delory, G. T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Andrews, David J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    McEnulty, T.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Morooka, M. W.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Stewart, A. I. F.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Mahaffy, P. R.
    NASA, Goddard Space Flight Ctr, Planetary Environm Lab, Code 699, Greenbelt, MD USA..
    Jakosky, B. M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Enhanced O-2(+) loss at Mars due to an ambipolar electric field from electron heating2016Ingår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, nr 5, s. 4668-4678Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent results from the MAVEN Langmuir Probe and Waves instrument suggest higher than predicted electron temperatures (T-e) in Mars' dayside ionosphere above similar to 180km in altitude. Correspondingly, measurements from Neutral Gas and Ion Mass Spectrometer indicate significant abundances of O-2(+) up to similar to 500km in altitude, suggesting that O-2(+) may be a principal ion loss mechanism of oxygen. In this article, we investigate the effects of the higher T-e (which results from electron heating) and ion heating on ion outflow and loss. Numerical solutions show that plasma processes including ion heating and higher T-e may greatly increase O-2(+) loss at Mars. In particular, enhanced T-e in Mars' ionosphere just above the exobase creates a substantial ambipolar electric field with a potential (e) of several k(B)T(e), which draws ions out of the region allowing for enhanced escape. With active solar wind, electron, and ion heating, direct O-2(+) loss could match or exceed loss via dissociative recombination of O-2(+). These results suggest that direct loss of O-2(+) may have played a significant role in the loss of oxygen at Mars over time.

  • 19.
    Ergun, R. E.
    et al.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Morooka, M. W.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Andersson, L. A.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Fowler, C. M.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Delory, G. T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Andrews, David J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    McEnulty, T.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Jakosky, B. M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Dayside electron temperature and density profiles at Mars: First results from the MAVEN Langmuir probe and waves instrument2015Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, nr 21, s. 8846-8853Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present Mars' electron temperature (T-e) and density (n(e)) altitude profiles derived from the MAVEN (Mars Atmosphere and Volatile EvolutioN) mission deep dip orbits in April 2015, as measured by the Langmuir probe instrument. These orbits had periapsides below 130 km in altitude at low solar zenith angles. The periapsides were above the peak in n(e) during this period. Using a Chapman function fit, we find that scale height and projected altitude of the n(e) peak are consistent with models and previous measurements. The peak electron density is slightly higher than earlier works. For the first time, we present in situ measurements of T-e altitude profiles in Mars' dayside in the altitude range from similar to 130 km to 500 km and provide a functional fit. Importantly, T-e rises rapidly with altitude from similar to 180 km to similar to 300 km. These results and functional fit are important for modeling Mars' ionosphere and understanding atmospheric escape.

  • 20.
    Eriksson, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för astronomi och rymdfysik.
    Engwall, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för astronomi och rymdfysik.
    Prakash, R.
    Daldorff, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för astronomi och rymdfysik.
    Torbert, R.
    Making use of spacecraft-plasma interactions: determining tenous plasma winds from wake observations and numerical simulations2007Ingår i: Proceedings of the 10th Spacecraft Charging Technology Conference, 2007Konferensbidrag (Övrigt vetenskapligt)
  • 21.
    Eriksson, Anders I.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Engelhardt, Ilka. A. D.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    André, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Boström, Rolf
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Edberg, Niklas J. T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Johansson, Fredrik L.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Vigren, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Wahlund, Jan-Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Henri, P.
    LPC2E, Lab Phys & Chim Environm & Espace.
    Lebreton, J. -P
    LPC2E, Lab Phys & Chim Environm & Espace.
    Miloch, W. J.
    Univ Oslo, Dept Phys.
    Paulsson, J. J. P.
    Univ Oslo, Dept Phys.
    Wedlund, Cyril Simon
    Univ Oslo, Dept Phys.
    Yang, L.
    Univ Oslo, Dept Phys.
    Karlsson, T.
    Royal Inst Technol, Alfvén Lab.
    Jarvinen, R.
    Finnish Meteorol Inst, Helsinki 00560.
    Broiles, Thomas
    Southwest Res Inst, San Antonio.
    Mandt, K.
    Southwest Res Inst, San Antonio; Univ Texas San Antonio, Dept Phys & Astron.
    Carr, C. M.
    Imperial Coll London, Dept Phys.
    Galand, M.
    Imperial Coll London, Dept Phys.
    Nilsson, H.
    Swedish Inst Space Phys, S-98128 Kiruna.
    Norberg, C.
    Swedish Inst Space Phys, S-98128 Kiruna.
    Cold and warm electrons at comet 67P/Churyumov-Gerasimenko2017Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 605, artikel-id A15Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. Strong electron cooling on the neutral gas in cometary comae has been predicted for a long time, but actual measurements of low electron temperature are scarce. Aims. Our aim is to demonstrate the existence of cold electrons in the inner coma of comet 67P/Churyumov-Gerasimenko and show filamentation of this plasma.

    Methods. In situ measurements of plasma density, electron temperature and spacecraft potential were carried out by the Rosetta Langmuir probe instrument, LAP. We also performed analytical modelling of the expanding two-temperature electron gas.

    Results. LAP data acquired within a few hundred km from the nucleus are dominated by a warm component with electron temperature typically 5-10 eV at all heliocentric distances covered (1.25 to 3.83 AU). A cold component, with temperature no higher than about 0.1 eV, appears in the data as short (few to few tens of seconds) pulses of high probe current, indicating local enhancement of plasma density as well as a decrease in electron temperature. These pulses first appeared around 3 AU and were seen for longer periods close to perihelion. The general pattern of pulse appearance follows that of neutral gas and plasma density. We have not identified any periods with only cold electrons present. The electron flux to Rosetta was always dominated by higher energies, driving the spacecraft potential to order -10 V.

    Conclusions. The warm (5-10 eV) electron population observed throughout the mission is interpreted as electrons retaining the energy they obtained when released in the ionisation process. The sometimes observed cold populations with electron temperatures below 0.1 eV verify collisional cooling in the coma. The cold electrons were only observed together with the warm population. The general appearance of the cold population appears to be consistent with a Haser-like model, implicitly supporting also the coupling of ions to the neutral gas. The expanding cold plasma is unstable, forming filaments that we observe as pulses.

  • 22.
    Fowler, C. M.
    et al.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Andersson, L.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Morooka, M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Delory, G.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Andrews, David J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Lillis, Robert J.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    McEnulty, T.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Weber, T. D.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Chamandy, T. M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Mitchell, D. L.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Mazelle, C.
    Inst Rech Astrophys & Planetol, CNRS, Toulouse, France.;Univ Toulouse 3, Inst Rech Astrophys & Planetol, F-31062 Toulouse, France..
    Jakosky, B. M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    The first in situ electron temperature and density measurements of the Martian nightside ionosphere2015Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, nr 21, s. 8854-8861Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The first in situ nightside electron density and temperature profiles at Mars are presented as functions of altitude and local time (LT) from the Langmuir Probe and Waves (LPW) instrument on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission spacecraft. LPW is able to measure densities as low as similar to 100 cm(-3), a factor of up to 10 or greater improvement over previous measurements. Above 200 km, near-vertical density profiles of a few hundred cubic centimeters were observed for almost all nightside LT, with the lowest densities and highest temperatures observed postmidnight. Density peaks of a few thousand cubic centimeters were observed below 200 km at all nightside LT. The lowest temperatures were observed below 180 km and approach the neutral atmospheric temperature. One-dimensional modeling demonstrates that precipitating electrons were able to sustain the observed nightside ionospheric densities below 200 km.

  • 23.
    Galand, M.
    et al.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Heritier, K. L.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Henri, P.
    Univ Orleans, CNRS, LPC2E, 3A,Ave Rech Sci, F-45071 Orleans 2, France..
    Broiles, T. W.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA..
    Allen, A. J.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Altwegg, K.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Beth, A.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Burch, J. L.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA..
    Carr, C. M.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Cupido, E.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Glassmeier, K. -H
    Johansson, Fredrik L.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Lebreton, J. -P
    Mandt, K. E.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA..
    Nilsson, H.
    Swedish Inst Space Phys, POB 812, SE-98128 Kiruna, Sweden..
    Richter, I.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Rubin, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Sagnieres, L. B. M.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Schwartz, S. J.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Semon, T.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Tzou, C. -Y
    Vallieres, X.
    Univ Orleans, CNRS, LPC2E, 3A,Ave Rech Sci, F-45071 Orleans 2, France..
    Vigren, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Wurz, P.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Ionospheric plasma of comet 67P probed by Rosetta at 3 au from the Sun2016Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, s. S331-S351Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We propose to identify the main sources of ionization of the plasma in the coma of comet 67P/Churyumov-Gerasimenko at different locations in the coma and to quantify their relative importance, for the first time, for close cometocentric distances (< 20 km) and large heliocentric distances (> 3 au). The ionospheric model proposed is used as an organizing element of a multi-instrument data set from the Rosetta Plasma Consortium (RPC) plasma and particle sensors, from the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis and from the Microwave Instrument on the Rosetta Orbiter, all on board the ESA/Rosetta spacecraft. The calculated ionospheric density driven by Rosetta observations is compared to the RPC-Langmuir Probe and RPC-Mutual Impedance Probe electron density. The main cometary plasma sources identified are photoionization of solar extreme ultraviolet (EUV) radiation and energetic electron-impact ionization. Over the northern, summer hemisphere, the solar EUV radiation is found to drive the electron density - with occasional periods when energetic electrons are also significant. Over the southern, winter hemisphere, photoionization alone cannot explain the observed electron density, which reaches sometimes higher values than over the summer hemisphere; electron-impact ionization has to be taken into account. The bulk of the electron population is warm with temperature of the order of 7-10 eV. For increased neutral densities, we show evidence of partial energy degradation of the hot electron energy tail and cooling of the full electron population.

  • 24. Garnier, P.
    et al.
    Wahlund, Jan-Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Holmberg, Madeleine K. G.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Rymd- och plasmafysik.
    Morooka, M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Grimald, S.
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Schippers, P.
    Gurnett, D. A.
    Krimigis, S. M.
    Krupp, N.
    Coates, A.
    Crary, F.
    Gustafsson, Georg
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    The detection of energetic electrons with the Cassini Langmuir probe at Saturn2012Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, s. A10202-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Cassini Langmuir probe, part of the Radio and Plasma Wave Science (RPWS) instrument, has provided a wealth of information about the cold and dense plasma in the Saturnian system. The analysis of the ion side current (current for negative potentials) measured by the probe from 2005 to 2008 reveals also a strong sensitivity to energetic electrons (250-450 eV). These electrons impact the surface of the probe, and generate a detectable current of secondary electrons. A broad secondary electrons current region is inferred from the observations in the dipole L Shell range of similar to 6-10, with a peak full width at half maximum (FWHM) at L = 6.4-9.4 (near the Dione and Rhea magnetic dipole L Shell values). This magnetospheric flux tube region, which displays a large day/night asymmetry, is related to the similar structure in the energetic electron fluxes as the one measured by the onboard Electron Spectrometer (ELS) of the Cassini Plasma Spectrometer (CAPS). It corresponds spatially to both the outer electron radiation belt observed by the Magnetosphere Imaging Instrument (MIMI) at high energies and to the low-energy peak which has been observed since the Voyager era. Finally, a case study suggests that the mapping of the current measured by the Langmuir probe for negative potentials can allow to identify the plasmapause-like boundary recently identified at Saturn, and thus potentially identify the separation between the closed and open magnetic field lines regions.

  • 25.
    Goetz, C.
    et al.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Koenders, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Hansen, K. C.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, 2455 Hayward St, Ann Arbor, MI 48109 USA..
    Burch, J.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA..
    Carr, C.
    Imperial Coll London, Space & Atmospher Phys Grp, Exhibit Rd, London SW7 2AZ, England..
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Fruehauff, D.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Guettler, C.
    Max Planck Inst Sonnensyst Forschung, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Henri, P.
    Univ Orleans, CNRS, UMR 7328, Lab Phys & Chim Environm & Espace, F-45100 Orleans, France..
    Nilsson, H.
    Swedish Inst Space Phys, POB 812, SE-98128 Kiruna, Sweden..
    Richter, I.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Rubin, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Sierks, H.
    Max Planck Inst Sonnensyst Forschung, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Tsurutani, B.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Volwerk, M.
    Austrian Acad Sci, Inst Weltraumforsch, Schmiedlstr 6, A-8042 Graz, Austria..
    Glassmeier, K. H.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany.;Max Planck Inst Sonnensyst Forschung, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Structure and evolution of the diamagnetic cavity at comet 67P/Churyumov-Gerasimenko2016Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, s. S459-S467Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The long duration of the Rosetta mission allows us to study the evolution of the diamagnetic cavity at comet 67P/Churyumov-Gerasimenko in detail. From 2015 April to 2016 February 665 intervals could be identified where Rosetta was located in a zero-magnetic-field region. We study the temporal and spatial distribution of this cavity and its boundary and conclude that the cavity properties depend on the long-term trend of the outgassing rate, but do not respond to transient events at the spacecraft location, such as outbursts or high neutral densities. Using an empirical model of the outgassing rate, we find a functional relationship between the outgassing rate and the distance of the cavity to the nucleus. There is also no indication that this unexpectedly large distance is related to unusual solar wind conditions. Because the deduced shape of the cavity boundary is roughly elliptical on small scales and the distances of the boundary from the nucleus are much larger than expected we conclude that the events observed by Rosetta are due to a moving instability of the cavity boundary itself.

  • 26.
    Goetz, C.
    et al.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Koenders, C.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Richter, I.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Altwegg, K.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Burch, J.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA..
    Carr, C.
    Univ London Imperial Coll Sci Technol & Med, Space & Atmospher Phys Grp, Exhibit Rd, London SW7 2AZ, England..
    Cupido, E.
    Univ London Imperial Coll Sci Technol & Med, Space & Atmospher Phys Grp, Exhibit Rd, London SW7 2AZ, England..
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Guettler, C.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Henri, P.
    Univ Orleans, CNRS, Lab Phys & Chim Environm & Espace, UMR 7328, F-45100 Orleans, France..
    Mokashi, P.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA..
    Nemeth, Z.
    Wigner Res Ctr Phys, Konkoly Thege Miklos Ut 29-33, H-1121 Budapest, Hungary..
    Nilsson, H.
    Swedish Inst Space Phys, POB 812, S-98128 Kiruna, Sweden..
    Rubin, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Sierks, H.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Tsurutani, B.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Vallat, C.
    European Space Astron Ctr, Madrid 28691, Spain..
    Volwerk, M.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria..
    Glassmeier, K. -H
    First detection of a diamagnetic cavity at comet 67P/Churyumov-Gerasimenko2016Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 588, artikel-id A24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. The Rosetta magnetometer RPC-MAG has been exploring the plasma environment of comet 67P/Churyumov-Gerasimenko since August 2014. The first months were dominated by low-frequency waves which evolved into more complex features. However, at the end of July 2015, close to perihelion, the magnetometer detected a region that did not contain any magnetic field at all. Aims. These signatures match the appearance of a diamagnetic cavity as was observed at comet 1P/Halley in 1986. The cavity here is more extended than previously predicted by models and features unusual magnetic field configurations, which need to be explained. Methods. The onboard magnetometer data were analyzed in detail and used to estimate the outgassing rate. A minimum variance analysis was used to determine boundary normals. Results. Our analysis of the data acquired by the Rosetta Plasma Consortium instrumentation confirms the existence of a diamagnetic cavity. The size is larger than predicted by simulations, however. One possible explanation are instabilities that are propagating along the cavity boundary and possibly a low magnetic pressure in the solar wind. This conclusion is supported by a change in sign of the Sun-pointing component of the magnetic field. Evidence also indicates that the cavity boundary is moving with variable velocities ranging from 230 500m/s.

  • 27.
    Goldstein, Raymond
    et al.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA.
    Burch, J. L.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA.
    Mokashi, P.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA.
    Mandt, K.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA.
    Carr, C.
    Imperial Coll, Blackett Lab, London SW7 2AZ, England.
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Glassmeier, K. -H
    Henri, P.
    Univ Orleans, CNRS, LPC3E, F-45071 Orleans 2, France.
    Nilsson, H.
    Swedish Inst Space Phys, SE-98128 Kiruna, Sweden.
    Rubin, M.
    Univ Bern, Inst Phys, CH-3012 Bern, Switzerland.
    Tzou, C. -Y
    Two years of solar wind and pickup ion measurements at comet 67P/Churyumov-Gerasimenko2017Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, s. S262-S267Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Ion and Electron Sensor (IES) as well as other members of the Rosetta Plasma Consortium (RPC) on board the Rosetta spacecraft (S/C) measured the characteristics of the solar wind almost continuously since its arrival at 67P/Churyumov-Gerasimenko (CG) in 2014 August. An important process at a comet is the so-called pickup process in which a newly ionized atom or molecule begins gyrating about the interplanetary magnetic field, is accelerated in the process and is carried along with the solar wind. Within a month after comet arrival, while Rosetta was < 100 km from CG, we began to observe low-energy (< 20 eV) positive ions. We believe that these are newly formed from cometary neutrals near Rosetta and attracted to the negative S/C potential. These ions were in the early phase of pickup and had not yet reached the energy they would after at least one full gyration about the magnetic field. As CG increased its activity, the flux and energy of the measured pickup ions increased intermittently while the solar wind appeared intermittently as well. By about 2015 end of April, the solar wind had become very faint until it eventually disappeared from the IES field of view. We then began to see ions at the highest energy levels of IES, > 10 keV for a few days and then intermittently through the remainder of the mission, but lower energy (a few keV) pickup ions were also observed. As of 2016 early February, the solar wind reappeared more consistently. We believe that the disappearance of the solar wind in the IES field of view is the result of interaction with the pickup ions and the eventual formation of a cavity that excluded the solar wind.

  • 28.
    Graham, Daniel B.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Vaivads, Andris
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Khotyaintsev, Yuri V.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    André, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Malaspina, D. M.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.
    Lindqvist, P-A
    KTH Royal Inst Technol, Sch Elect Engn, Space & Plasma Phys, Stockholm, Sweden.
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA;Univ Maryland, Dept Astron, College Pk, MD 20742 USA.
    Plaschke, F.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Enhanced Escape of Spacecraft Photoelectrons Caused by Langmuir and Upper Hybrid Waves2018Ingår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, nr 9, s. 7534-7553Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The spacecraft potential is often used to infer rapid changes in the thermal plasma density. The variations in spacecraft potential associated with large-amplitude Langmuir and upper hybrid waves are investigated with the Magnetospheric Multiscale (MMS) mission. When large-amplitude Langmuir and upper hybrid waves are observed, the spacecraft potential increases. The changes in spacecraft potential are shown to be due to enhanced photoelectron escape from the spacecraft when the wave electric fields reach large amplitude. The fluctuations in spacecraft potential follow the envelope function of the Langmuir and upper hybrid waves. Comparison with the high-resolution electron moments shows that the changes in spacecraft potential associated with the waves are not due to density perturbations. Indeed, using the spacecraft potential as a density probe leads to unphysically large density fluctuations. In addition, the changes in spacecraft potential are shown to increase as density decreases: larger spacecraft potential changes are observed in the magnetosphere, than in the magnetosheath and solar wind. These results show that external electric fields can lead to unphysical results when the spacecraft potential is used as a density probe. The results suggest that fluctuations in the spacecraft potential alone cannot be used to determine whether nonlinear processes associated with Langmuir and upper hybrid waves, such as the ponderomotive force and three-wave decay, are occurring.

  • 29.
    Grun, E.
    et al.
    Max Planck Inst Kernphys, Saupfercheckweg 1, D-69127 Heidelberg, Germany.;Univ Colorado, Lab Atmospher & Space Phys, 1234 Innovat Dr, Boulder, CO 80303 USA..
    Agarwal, J.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Altobelli, N.
    ESA, Camino Bajo Castillo S-N, E-28692 Madrid, Spain..
    Altwegg, K.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Bentley, M. S.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria..
    Biver, N.
    Univ Paris Diderot, UPMC, CNRS, LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Della Corte, V.
    INAF, IAPS, Via Fosso Cavaliere, I-00133 Rome, Italy..
    Edberg, Niklas J. T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Feldman, P. D.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA..
    Galand, M.
    Imperial Coll, South Kensington Campus, London SW7 2AZ, England..
    Geiger, B.
    ESA, Camino Bajo Castillo S-N, E-28692 Madrid, Spain..
    Goetz, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, D-38106 Braunschweig, Germany..
    Grieger, B.
    ESA, Camino Bajo Castillo S-N, E-28692 Madrid, Spain..
    Guettler, C.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Henri, P.
    CNRS, LPC2E, Orleans, France..
    Hofstadter, M.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Horanyi, M.
    Univ Colorado, Lab Atmospher & Space Phys, 1234 Innovat Dr, Boulder, CO 80303 USA..
    Jehin, E.
    Univ Liege, Inst Astrophys & Geophys, B-4000 Liege, Belgium..
    Krueger, H.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Lee, S.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Mannel, T.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria..
    Morales, E.
    Jaicoa Observ, Aguadilla, PR USA..
    Mousis, O.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, F-13388 Marseille, France..
    Mueller, M.
    ESOC, ESA, Robert Bosch Str 5, Darmstadt, Germany..
    Opitom, C.
    Univ Liege, Inst Astrophys & Geophys, B-4000 Liege, Belgium..
    Rotundi, A.
    INAF, IAPS, Via Fosso Cavaliere, I-00133 Rome, Italy.;Univ Napoli Parthenope, Dip Sci & Tecnol, CDN IC4, I-80143 Naples, Italy..
    Schmied, R.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria.;Graz Univ, Inst Phys, Univ Pl 3, A-8010 Graz, Austria..
    Schmidt, F.
    Univ Stuttgart, Inst Raumfahrtsyst IRS, Pfaffenwaldring 29, D-70569 Stuttgart, Germany..
    Sierks, H.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Snodgrass, C.
    Open Univ, Dept Phys Sci, Planetary & Space Sci, Milton Keynes MK7 6AA, Bucks, England..
    Soja, R. H.
    Univ Stuttgart, Inst Raumfahrtsyst IRS, Pfaffenwaldring 29, D-70569 Stuttgart, Germany..
    Sommer, M.
    Univ Stuttgart, Inst Raumfahrtsyst IRS, Pfaffenwaldring 29, D-70569 Stuttgart, Germany..
    Srama, R.
    Univ Stuttgart, Inst Raumfahrtsyst IRS, Pfaffenwaldring 29, D-70569 Stuttgart, Germany..
    Tzou, C. -Y
    Vincent, J. -B
    Yanamandra-Fisher, P.
    Space Sci Inst, 13456 Cajon Creek Court, Rancho Cucamonga, CA 91739 USA..
    A'Hearn, M. F.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Barbieri, C.
    Univ Padua, Dept Phys & Astron G Galilei, Vic Osservatorio 3, I-35122 Padua, Italy..
    Barucci, M. A.
    Univ Paris Diderot, UPMC, CNRS, LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Bertaux, J. -L
    Bertini, I.
    Univ Padua, Ctr Ateneo Studi Attivita Spaziali Giusepp Colomb, Via Venezia 15, I-35131 Padua, Italy..
    Burch, J.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Colangeli, L.
    European Space Agcy, European Space Res & Technol Ctr, Keplerlaan 1, NL-2201 AZ Noordwijk, Netherlands..
    Cremonese, G.
    Osserv Astron Padova, INAF, Vicolo Osservatorio 5, I-35122 Padua, Italy..
    Da Deppo, V.
    CNR, IFN UOS Padova LUXOR, Via Trasea 7, I-35131 Padua, Italy..
    Davidsson, Björn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Teoretisk astrofysik.
    Debei, S.
    Univ Padua, Dept Ind Engn, Via Venezia 1, I-35131 Padua, Italy..
    De Cecco, M.
    Osserv Astron Trieste, INAF, Via Tiepolo 11, I-34143 Trieste, Italy..
    Deller, J.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Feaga, L. M.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Ferrari, M.
    INAF, IAPS, Via Fosso Cavaliere, I-00133 Rome, Italy..
    Fornasier, S.
    Univ Paris Diderot, UPMC, CNRS, LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Fulle, M.
    Osserv Astron Trieste, INAF, Via Tiepolo 11, I-34143 Trieste, Italy..
    Gicquel, A.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Gillon, M.
    Univ Liege, Inst Astrophys & Geophys, B-4000 Liege, Belgium..
    Green, S. F.
    Open Univ, Dept Phys Sci, Planetary & Space Sci, Milton Keynes MK7 6AA, Bucks, England..
    Groussin, O.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, F-13388 Marseille, France..
    Gutierrez, P. J.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron, E-18008 Granada, Spain..
    Hofmann, M.
    Hviid, S. F.
    DLR, Inst Planetary Res, Rutherfordstr 2, D-12489 Berlin, Germany..
    Ip, W. -H
    Ivanovski, S.
    INAF, IAPS, Via Fosso Cavaliere, I-00133 Rome, Italy..
    Jorda, L.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, F-13388 Marseille, France..
    Keller, H. U.
    TU Braunschweig, Inst Geophys & Extraterr Phys, D-38106 Braunschweig, Germany..
    Knight, M. M.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Knollenberg, J.
    DLR, Inst Planetary Res, Rutherfordstr 2, D-12489 Berlin, Germany..
    Koschny, D.
    European Space Agcy, European Space Res & Technol Ctr, Keplerlaan 1, NL-2201 AZ Noordwijk, Netherlands..
    Kramm, J. -R
    Kuehrt, E.
    DLR, Inst Planetary Res, Rutherfordstr 2, D-12489 Berlin, Germany..
    Kuppers, M.
    ESA, Camino Bajo Castillo S-N, E-28692 Madrid, Spain..
    Lamy, P. L.
    CNRS, UMR 7326, Lab Astrophys Marseille, 38 Rue Federic Joliot Curie, F-13388 Marseille 13, France.;Aix Marseille Univ, 38 Rue Federic Joliot Curie, F-13388 Marseille 13, France..
    Lara, L. M.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron, E-18008 Granada, Spain..
    Lazzarin, M.
    Univ Padua, Dept Phys & Astron G Galilei, Vic Osservatorio 3, I-35122 Padua, Italy..
    Lopez-Moreno, J. J.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, E-18008 Granada, Spain..
    Manfroid, J.
    Univ Liege, Inst Astrophys & Geophys, B-4000 Liege, Belgium..
    Epifani, E. Mazzotta
    OAR, INAF, Via Frascati 33, I-00078 Rome, Italy..
    Marzari, F.
    Univ Padua, Dept Phys & Astron G Galilei, Vic Osservatorio 3, I-35122 Padua, Italy..
    Naletto, G.
    Univ Padua, Ctr Ateneo Studi Attivita Spaziali Giusepp Colomb, Via Venezia 15, I-35131 Padua, Italy.;Univ Padua, Dept Informat Engn, Via Gradenigo 6-B, I-35131 Padua, Italy..
    Oklay, N.
    Palumbo, P.
    INAF, IAPS, Via Fosso Cavaliere, I-00133 Rome, Italy.;Univ Napoli Parthenope, Dip Sci & Tecnol, CDN IC4, I-80143 Naples, Italy..
    Parker, J. Wm.
    Southwest Res Inst, 1050 Walnut St,Suite 300, Boulder, CO 80302 USA..
    Rickman, Hans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Teoretisk astrofysik. PAS Space Res Ctr, Poland.
    Rodrigo, R.
    ESA, Camino Bajo Castillo S-N, E-28692 Madrid, Spain.;Int Space Sci Inst, Hallerstr 6, CH-3012 Bern, Switzerland..
    Rodriguez, J.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, E-18008 Granada, Spain..
    Schindhelm, E.
    Southwest Res Inst, 1050 Walnut St,Suite 300, Boulder, CO 80302 USA..
    Shi, X.
    Sordini, R.
    INAF, IAPS, Via Fosso Cavaliere, I-00133 Rome, Italy..
    Steffl, A. J.
    Southwest Res Inst, 1050 Walnut St,Suite 300, Boulder, CO 80302 USA..
    Stern, S. A.
    Southwest Res Inst, 1050 Walnut St,Suite 300, Boulder, CO 80302 USA..
    Thomas, N.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Tubiana, C.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Weaver, H. A.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Weissman, P.
    Planetary Sci Inst, 1700 East Ft Lowell,Suite 106, Tucson, AZ 85719 USA..
    Zakharov, V. V.
    Univ Paris Diderot, UPMC, CNRS, LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France.;UPMC Univ Paris 06, CNRS, Sorbonne Univ, Lab Meteorol Dynam, 4 Pl Jussieu, F-75252 Paris, France..
    The 2016 Feb 19 outburst of comet 67P/CG: an ESA Rosetta multi-instrument study2016Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, s. S220-S234Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    On 2016 Feb 19, nine Rosetta instruments serendipitously observed an outburst of gas and dust from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras and spectrometers ranging from UV over visible to microwave wavelengths, in situ gas, dust and plasma instruments, and one dust collector. At 09: 40 a dust cloud developed at the edge of an image in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature of the outburst that significantly exceeded the background. The enhancement ranged from 50 per cent of the neutral gas density at Rosetta to factors > 100 of the brightness of the coma near the nucleus. Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest enhancements (factors > 10). However, even the electron density at Rosetta increased by a factor 3 and consequently the spacecraft potential changed from similar to-16 V to -20 V during the outburst. A clear sequence of events was observed at the distance of Rosetta ( 34 km from the nucleus): within 15 min the Star Tracker camera detected fast particles (similar to 25 m s(-1)) while 100 mu m radius particles were detected by the GIADA dust instrument similar to 1 h later at a speed of 6 m s(-1). The slowest were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst originated just outside the FOV of the instruments, the source region and the magnitude of the outburst could be determined.

  • 30.
    Gunell, H.
    et al.
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium;Umea Univ, Dept Phys, SE-90187 Umea, Sweden.
    Goetz, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Nilsson, H.
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden.
    Wedlund, C. Simon
    Univ Oslo, Dept Phys, Box 1048 Blindern, N-0316 Oslo, Norway.
    Henri, P.
    CNRS, LPC2E, F-45071 Orleans, France.
    Maggiolo, R.
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium.
    Hamrin, M.
    Umea Univ, Dept Phys, SE-90187 Umea, Sweden.
    De Keyser, J.
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium.
    Rubin, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Wieser, G. Stenberg
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden.
    Cessateur, G.
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium.
    Dhooghe, F.
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium.
    Gibbons, A.
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium;Univ Libre Bruxelles, Lab Chim Quant & Photophys, 50 Ave FD Roosevelt, B-1050 Brussels, Belgium.
    Plasma waves confined to the diamagnetic cavity of comet 67P/Churyumov-Gerasimenko2017Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, s. S84-S92Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ion acoustic waves were observed in the diamagnetic cavity of comet 67P/Churyumov-Gerasimenko by the Rosetta spacecraft on 2015 August 3, when the comet was 1.25 au from the Sun. Wave spectra recorded by the Langmuir probe (RPC-LAP), peak near 200 Hz, decrease for higher frequencies and reach the noise floor at approximately 1.5 kHz. These waves were observed only when the spacecraft was in the diamagnetic cavity or at its boundary, which is identified as a sharp drop in magnetic field magnitude, measured by RPC-MAG. The plasma, on both sides of the boundary, is dominated by a cold (a few hundred K) water group ion population, one cold (k(B)T(e) similar to 0.1 eV) and one warm (k(B)T(e) similar to 10 eV) electron population. The observations are interpreted in terms of current-driven ion acoustic waves, generated by currents that flow through bulges on the boundary of the diamagnetic cavity.

  • 31.
    Gunell, H.
    et al.
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium..
    Nilsson, H.
    Swedish Inst Space Phys, POB 812, S-98128 Kiruna, Sweden..
    Hamrin, M.
    Umea Univ, Dept Phys, S-90187 Umea, Sweden..
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Rymd- och plasmafysik.
    Maggiolo, R.
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium..
    Henri, P.
    CNRS, LPC2E, F-45071 Orleans, France..
    Vallieres, X.
    CNRS, LPC2E, F-45071 Orleans, France..
    Altwegg, K.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Tzou, C. -Y
    Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland .
    Rubin, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Glassmeier, K. -H
    Institut für Geophysik und extraterrestrische Physik, TU Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany .
    Wieser, G. Stenberg
    Swedish Inst Space Phys, POB 812, S-98128 Kiruna, Sweden..
    Wedlund, C. Simon
    Univ Oslo, Dept Phys, Box 1048 Blindern, N-0316 Oslo, Norway..
    De Keyser, J.
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium..
    Dhooghe, F.
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium..
    Cessateur, G.
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium..
    Gibbons, A.
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium.;Univ Libre Bruxelles, Lab Chim Quant & Photophys, 50 Ave FD Roosevelt, B-1050 Brussels, Belgium..
    Ion acoustic waves at comet 67P/Churyumov-Gerasimenko: Observations and computations2017Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 600, artikel-id A3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. On 20 January 2015 the Rosetta spacecraft was at a heliocentric distance of 2.5 AU, accompanying comet 67P/Churyumov-Gerasimenko on its journey toward the Sun. The Ion Composition Analyser (RPC-ICA), other instruments of the Rosetta Plasma Consortium, and the ROSINA instrument made observations relevant to the generation of plasma waves in the cometary environment.

    Aims. Observations of plasma waves by the Rosetta Plasma Consortium Langmuir probe (RPC-LAP) can be explained by dispersion relations calculated based on measurements of ions by the Rosetta Plasma Consortium Ion Composition Analyser (RPC-ICA), and this gives insight into the relationship between plasma phenomena and the neutral coma, which is observed by the Comet Pressure Sensor of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis instrument (ROSINA-COPS).

    Methods. We use the simple pole expansion technique to compute dispersion relations for waves on ion timescales based on the observed ion distribution functions. These dispersion relations are then compared to the waves that are observed. Data from the instruments RPC-LAP, RPC-ICA and the mutual impedance probe (RPC-MIP) are compared to find the best estimate of the plasma density.

    Results. We find that ion acoustic waves are present in the plasma at comet 67P/Churyumov-Gerasimenko, where the major ion species is H2O+. The bulk of the ion distribution is cold, k(B)T(i) = 0.01 eV when the ion acoustic waves are observed. At times when the neutral density is high, ions are heated through acceleration by the solar wind electric field and scattered in collisions with the neutrals. This process heats the ions to about 1 eV, which leads to significant damping of the ion acoustic waves.

    Conclusions. In conclusion, we show that ion acoustic waves appear in the H2O+ plasmas at comet 67P/Churyumov-Gerasimenko and how the interaction between the neutral and ion populations affects the wave properties.

  • 32.
    Gunell, Herbert
    et al.
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium;Umea Univ, Dept Phys, S-90187 Umea, Sweden.
    Goetz, Charlotte
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany.
    Wedlund, Cyril Simon
    Univ Oslo, Dept Phys, Box 1048 Blindern, N-0316 Oslo, Norway.
    Lindkvist, Jesper
    Umea Univ, Dept Phys, S-90187 Umea, Sweden.
    Hamrin, Maria
    Umea Univ, Dept Phys, S-90187 Umea, Sweden.
    Nilsson, Hans
    Swedish Inst Space Phys, Box 812, S-98128 Kiruna, Sweden.
    LLera, Kristie
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA.
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Holmström, Mats
    Swedish Inst Space Phys, Box 812, S-98128 Kiruna, Sweden.
    The infant bow shock: a new frontier at a weak activity comet2018Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 619, artikel-id L2Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The bow shock is the first boundary the solar wind encounters as it approaches planets or comets. The Rosetta spacecraft was able to observe the formation of a bow shock by following comet 67P/Churyumov-Gerasimenko toward the Sun, through perihelion, and back outward again. The spacecraft crossed the newly formed bow shock several times during two periods a few months before and after perihelion; it observed an increase in magnetic field magnitude and oscillation amplitude, electron and proton heating at the shock, and the diminution of the solar wind further downstream. Rosetta observed a cometary bow shock in its infancy, a stage in its development not previously accessible to in situ measurements at comets and planets.

  • 33.
    Haaland, S.
    et al.
    Univ Bergen, Birkeland Ctr Space Sci, Bergen, Norway.;Max Planck Inst Solar Syst Res, Gottingen, Germany..
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    André, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Maes, L.
    Belgian Inst Aeron, Brussels, Belgium..
    Baddeley, L.
    Univ Ctr Svalbard, Dept Arctic Geophys, Longyearbyen, Norway..
    Barakat, A.
    Utah State Univ, Ctr Atmospher & Space Sci, Logan, UT 84322 USA..
    Chappell, R.
    Vanderbilt Univ, Sci & Res Commun, Nashville, TN 37235 USA..
    Eccles, V.
    Utah State Univ, Ctr Atmospher & Space Sci, Logan, UT 84322 USA..
    Johnsen, C.
    Univ Oslo, Dept Geophys, Oslo, Norway..
    Lybekk, B.
    Univ Oslo, Dept Phys, Oslo, Norway..
    Li, K.
    Max Planck Inst Solar Syst Res, Gottingen, Germany..
    Pedersen, A.
    Univ Oslo, Dept Phys, Oslo, Norway..
    Schunk, R.
    Utah State Univ, Ctr Atmospher & Space Sci, Logan, UT 84322 USA..
    Welling, D.
    Univ Bergen, Birkeland Ctr Space Sci, Bergen, Norway.;Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA..
    Estimation of cold plasma outflow during geomagnetic storms2015Ingår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, nr 12, s. 10622-10639Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low-energy ions of ionospheric origin constitute a significant contributor to the magnetospheric plasma population. Measuring cold ions is difficult though. Observations have to be done at sufficiently high altitudes and typically in regions of space where spacecraft attain a positive charge due to solar illumination. Cold ions are therefore shielded from the satellite particle detectors. Furthermore, spacecraft can only cover key regions of ion outflow during segments of their orbit, so additional complications arise if continuous longtime observations, such as during a geomagnetic storm, are needed. In this paper we suggest a new approach, based on a combination of synoptic observations and a novel technique to estimate the flux and total outflow during the various phases of geomagnetic storms. Our results indicate large variations in both outflow rates and transport throughout the storm. Prior to the storm main phase, outflow rates are moderate, and the cold ions are mainly emanating from moderately sized polar cap regions. Throughout the main phase of the storm, outflow rates increase and the polar cap source regions expand. Furthermore, faster transport, resulting from enhanced convection, leads to a much larger supply of cold ions to the near-Earth region during geomagnetic storms.

  • 34. Haaland, S.
    et al.
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Engwall, E.
    Lybekk, B.
    Nilsson, H.
    Pedersen, A.
    Svenes, K.
    André, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Foerster, M.
    Li, K.
    Johnsen, C.
    Ostgaard, N.
    Estimating the capture and loss of cold plasma from ionospheric outflow2012Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, s. A07311-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An important source of magnetospheric plasma is cold plasma from the terrestrial ionosphere. Low energy ions travel along the magnetic field lines and enter the magnetospheric lobes where they are convected toward the tail plasma sheet. Recent observations indicate that the field aligned ion outflow velocity is sometimes much higher than the convection toward the central plasma sheet. A substantial amount of plasma therefore escapes downtail without ever reaching the central plasma sheet. In this work, we use Cluster measurements of cold plasma outflow and lobe convection velocities combined with models of the magnetic field in an attempt to determine the fate of the outflowing ions and to quantify the amount of plasma lost downtail. The results show that both the circulation of plasma and the direct tailward escape of ions varies significantly with magnetospheric conditions. For strong solar wind driving with a southward interplanetary magnetic field, also typically associated with high geomagnetic activity, most of the outflowing plasma is convected to the plasma sheet and recirculated. For periods with northward interplanetary magnetic field, the convection is nearly stagnant, whereas the outflow, although limited, still persists. The dominant part of the outflowing ions escape downtail and are directly lost into the solar wind under such conditions.

  • 35.
    Hajra, R.
    et al.
    CNRS, LPC2E, Orleans, France..
    Henri, P.
    CNRS, LPC2E, Orleans, France..
    Vallieres, X.
    CNRS, LPC2E, Orleans, France..
    Galand, M.
    Imperial Coll, South Kensington Campus, London SW7 2AZ, England..
    Heritier, K.
    Imperial Coll, South Kensington Campus, London SW7 2AZ, England..
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Edberg, Niklas J. T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Burch, J. L.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA..
    Broiles, T.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA..
    Goldstein, R.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA..
    Glassmeier, K. H.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Richter, I.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Goetz, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Tsurutani, B. T.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Nilsson, H.
    Swedish Inst Space Phys, POB 812, S-98128 Kiruna, Sweden..
    Altwegg, K.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Rubin, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Impact of a cometary outburst on its ionosphere Rosetta Plasma Consortium observations of the outburst exhibited by comet 67P/Churyumov-Gerasimenko on 19 February 20162017Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 607, artikel-id A34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a detailed study of the cometary ionospheric response to a cometary brightness outburst using in situ measurements for the first time. The comet 67P/Churyumov-Gerasimenko (67P) at a heliocentric distance of 2.4 AU from the Sun, exhibited an outburst at similar to 1000 UT on 19 February 2016, characterized by an increase in the coma surface brightness of two orders of magnitude. The Rosetta spacecraft monitored the plasma environment of 67P from a distance of 30 km, orbiting with a relative speed of similar to 0.2 m s(-1). The onset of the outburst was preceded by pre-outburst decreases in neutral gas density at Rosetta, in local plasma density, and in negative spacecraft potential at similar to 0950 UT. In response to the outburst, the neutral density increased by a factor of similar to 1.8 and the local plasma density increased by a factor of similar to 3, driving the spacecraft potential more negative. The energetic electrons (tens of eV) exhibited decreases in the flux of factors of similar to 2 to 9, depending on the energy of the electrons. The local magnetic field exhibited a slight increase in amplitude (similar to 5 nT) and an abrupt rotation (similar to 36.4 degrees) in response to the outburst. A weakening of 10-100 mHz magnetic field fluctuations was also noted during the outburst, suggesting alteration of the origin of the wave activity by the outburst. The plasma and magnetic field effects lasted for about 4 h, from similar to 1000 UT to 1400 UT. The plasma densities are compared with an ionospheric model. This shows that while photoionization is the main source of electrons, electron-impact ionization and a reduction in the ion outflow velocity need to be accounted for in order to explain the plasma density enhancement near the outburst peak.

  • 36.
    Hajra, Rajkumar
    et al.
    CNRS, LPC2E, F-45071 Orleans, France.
    Henri, Pierre
    CNRS, LPC2E, F-45071 Orleans, France.
    Myllys, Minna
    CNRS, LPC2E, F-45071 Orleans, France.
    Heritier, Kevin L.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Galand, Marina
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Wedlund, Cyril Simon
    Univ Oslo, Dept Phys, Box 1048 Blindern, N-0316 Oslo, Norway.
    Breuillard, Hugo
    CNRS, LPC2E, F-45071 Orleans, France;Sorbonne Univ, CNRS, Ecole Polytech, Lab Phys Plasmas, 4 Pl Jussieu, F-75252 Paris, France.
    Behar, Etienne
    Swedish Inst Space Phys, POB 812, SE-98128 Kiruna, Sweden.
    Edberg, Niklas J. T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Goetz, Charlotte
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany.
    Nilsson, Hans
    Swedish Inst Space Phys, POB 812, SE-98128 Kiruna, Sweden.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Goldstein, Raymond
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA.
    Tsurutani, Bruce T.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA.
    More, Jerome
    CNRS, LPC2E, F-45071 Orleans, France.
    Vallieres, Xavier
    CNRS, LPC2E, F-45071 Orleans, France.
    Wattieauxu, Gaetan
    Univ Toulouse, CNRS, LAPLACE, F-31062 Toulouse, France.
    Cometary plasma response to interplanetary corotating interaction regions during 2016 June-September: a quantitative study by the Rosetta Plasma Consortium2018Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 480, nr 4, s. 4544-4556Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Four interplanetary corotating interaction regions (CIRs) were identified during 2016 June-September by the Rosetta Plasma Consortium (RPC) monitoring in situ the plasma environment of the comet 67P/Churyumov-Gerasimenko (67P) at heliocentric distances of similar to 3-3.8 au. The CIRs, formed in the interface region between low- and high-speed solar wind streams with speeds of similar to 320-400 km s(-1) and similar to 580-640 km s(-1), respectively, are characterized by relative increases in solar wind proton density by factors of similar to 13-29, in proton temperature by similar to 7-29, and in magnetic field by similar to 1-4 with respect to the pre-CIR values. The CIR boundaries are well defined with interplanetary discontinuities. Out of 10 discontinuities, four are determined to be forward waves and five are reverse waves, propagating at similar to 5-92 per cent of the magnetosonic speed at angles of similar to 20 degrees-87 degrees relative to ambient magnetic field. Only one is identified to be a quasi-parallel forward shock with magnetosonic Mach number of similar to 1.48 and shock normal angle of similar to 41 degrees. The cometary ionosphere response was monitored by Rosetta from cometocentric distances of similar to 4-30 km. A quiet time plasma density map was developed by considering dependences on cometary latitude, longitude, and cometocentric distance of Rosetta observations before and after each of the CIR intervals. The CIRs lead to plasma density enhancements of similar to 500-1000 per cent with respect to the quiet time reference level. Ionospheric modelling shows that increased ionization rate due to enhanced ionizing (>12-200 eV) electron impact is the prime cause of the large cometary plasma density enhancements during the CIRs. Plausible origin mechanisms of the cometary ionizing electron enhancements are discussed.

  • 37.
    Hajra, Rajkumar
    et al.
    CNRS, LPC2E, F-45071 Orleans, France.
    Henri, Pierre
    CNRS, LPC2E, F-45071 Orleans, France.
    Vallieres, Xavier
    CNRS, LPC2E, F-45071 Orleans, France.
    More, Jerome
    CNRS, LPC2E, F-45071 Orleans, France.
    Gilet, Nicolas
    CNRS, LPC2E, F-45071 Orleans, France.
    Wattieaux, Gaetan
    Univ Toulouse, LAPLACE, CNRS, F-31062 Toulouse, France.
    Goetz, Charlotte
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany.
    Richter, Ingo
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany.
    Tsurutani, Bruce T.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA.
    Gunell, Herbert
    Royal Belgian Inst Space Aeron BIRA IASB, Ave Circulaire 3, B-1180 Brussels, Belgium;Umea Univ, Dept Phys, SE-90187 Umea, Sweden.
    Nilsson, Hans
    Swedish Inst Space Phys, POB 812, SE-98128 Kiruna, Sweden.
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Nemeth, Zoltan
    Wigner Res Ctr Phys, Konkoly Thege M Rd 29-33, Budapest, Hungary.
    Burchdegrees, James L.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA.
    Rubin, Martin
    Univ Bern, Inst Phys, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Dynamic unmagnetized plasma in the diamagnetic cavity around comet 67P/Churyumov-Gerasimenko2018Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 475, nr 3, s. 4140-4147Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Rosetta orbiter witnessed several hundred diamagnetic cavity crossings (unmagnetized regions) around comet 67P/Churyumov-Gerasimenko during its two year survey of the comet. The characteristics of the plasma environment inside these diamagnetic regions are studied using in situ measurements by the Rosetta Plasma Consortium instruments. Although the unmagnetized plasma density has been observed to exhibit little dynamics compared to the very dynamical magnetized cometary plasma, we detected several localized dynamic plasma structures inside those diamagnetic regions. These plasma structures are not related to the direct ionization of local cometary neutrals. The structures are found to be steepened, asymmetric plasma enhancements with typical rising-to-descending slope ratio of similar to 2.8 (+/- 1.9), skewness similar to 0.43 (+/- 0.36), mean duration of similar to 2.7 (+/- 0.9) min and relative density variation Delta N/N of similar to 0.5 (+/- 0.2), observed close to the electron exobase. Similar steepened plasma density enhancements were detected at the magnetized boundaries of the diamagnetic cavity as well as outside the diamagnetic region. The plausible scalelength and propagation direction of the structures are estimated from simple plasma dynamics considerations. It is suggested that they are large-scale unmagnetized plasma enhancements, transmitted from the very dynamical outer magnetized region to the inner magnetic field-free cavity region.

  • 38.
    Hall, Jan-Ove
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för astronomi och rymdfysik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Leyser, Thomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Excitation of localized rotating waves in plasma density cavities by scattering of fast magnetosonic waves2004Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 92, nr 25 pt.1, s. 255002-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An analytic description of electromagnetic waves in an inhomogeneous plasma is applied to investigate excitation of localized rotating waves below the lower hybrid frequency through scattering of fast magnetosonic waves on a density cavity. The magnetosonic wave is focused to left-handed rotating oscillations. We find the amplitude of the localized oscillations, resonance frequencies, and the width of the resonances. The theory is relevant for the lower hybrid solitary structures observed in space plasmas and is shown to be consistent with observations by the Freja satellite.

  • 39.
    Henri, P.
    et al.
    CNRS, LPC2E, F-45071 Orleans, France;CNRS, LPC2E, 3A Ave Rech Sci, F-45071 Orleans, France.
    Vallieres, X.
    CNRS, LPC2E, F-45071 Orleans, France.
    Hajra, R.
    CNRS, LPC2E, F-45071 Orleans, France.
    Goetz, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany.
    Richter, I.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany.
    Glassmeier, K. -H
    Galand, M.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Rubin, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Nemeth, Z.
    Wigner Res Ctr Phys, Budapest, Hungary.
    Vigren, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Beth, A.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Burch, J. L.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA.
    Carr, C.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Nilsson, H.
    Swedish Inst Space Phys, POB 812, SE-98128 Kiruna, Sweden.
    Tsurutani, B.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA.
    Wattieaux, G.
    Univ Toulouse, CNRS, LAPLACE, F-31062 Toulouse, France.
    Diamagnetic region(s): structure of the unmagnetized plasma around Comet 67P/CG2017Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, s. S372-S379Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ESA's comet chaser Rosetta has monitored the evolution of the ionized atmosphere of comet 67P/Churyumov-Gerasimenko (67P/CG) and its interaction with the solar wind, during more than 2 yr. Around perihelion, while the cometary outgassing rate was highest, Rosetta crossed hundreds of unmagnetized regions, but did not seem to have crossed a large-scale diamagnetic cavity as anticipated. Using in situ Rosetta observations, we characterize the structure of the unmagnetized plasma found around comet 67P/CG. Plasma density measurements from RPC-MIP are analysed in the unmagnetized regions identified with RPC-MAG. The plasma observations are discussed in the context of the cometary escaping neutral atmosphere, observed by ROSINA/COPS. The plasma density in the different diamagnetic regions crossed by Rosetta ranges from similar to 100 to similar to 1500 cm(-3). They exhibit a remarkably systematic behaviour that essentially depends on the comet activity and the cometary ionosphere expansion. An effective total ionization frequency is obtained from in situ observations during the high outgassing activity phase of comet 67P/CG. Although several diamagnetic regions have been crossed over a large range of distances to the comet nucleus (from 50 to 400 km) and to the Sun (1.25-2.4 au), in situ observations give strong evidence for a single diamagnetic region, located close to the electron exobase. Moreover, the observations are consistent with an unstable contact surface that can locally extend up to about 10 times the electron exobase.

  • 40.
    Heritier, K. L.
    et al.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Altwegg, K.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Balsiger, H.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Berthelier, J. -J
    Beth, A.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Bieler, A.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Biver, N.
    Univ Paris Diderot, UPMC Univ Paris 06, Sorbonne Univ, CNRS,PSL Res Univ,Observat Paris,LESIA, Sorbonne Paris Cite,5 Pl Jules Janssen, F-92195 Meudon, France.
    Calmonte, U.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Combi, M. R.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA.
    De Keyser, J.
    Royal Belgian Inst Space Aeron, BIRA IASB, Ringlaan 3, B-1180 Brussels, Belgium.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Fiethe, B.
    TU Braunschweig, Inst Comp & Network Engn IDA, D-38106 Braunschweig, Germany.
    Fougere, N.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA.
    Fuselier, S. A.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA;Univ Texas San Antonio, San Antonio, TX 78249 USA.
    Galand, M.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Gasc, S.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Gombosi, T. I.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA.
    Hansen, K. C.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA.
    Hassig, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland;Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA.
    Kopp, E.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Rubin, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Tzou, C. -Y
    Vigren, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Vuitton, V.
    Univ Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France.
    Ion composition at comet 67P near perihelion: Rosetta observations and model-based interpretation2017Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, s. S427-S442Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the ion composition in the coma of comet 67P with newly detected ion species over the 28-37 u mass range, probed by Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA)/Double Focusing Mass Spectrometer (DFMS). In summer 2015, the nucleus reached its highest outgassing rate and ion-neutral reactions started to take place at low cometocentric distances. Minor neutrals can efficiently capture protons from the ion population, making the protonated version of these neutrals a major ion species. So far, only NH4+ has been reported at comet 67P. However, there are additional neutral species with proton affinities higher than that of water (besides NH3) that have been detected in the coma of comet 67P: CH3OH, HCN, H2CO and H2S. Their protonated versions have all been detected. Statistics showing the number of detections with respect to the number of scans are presented. The effect of the negative spacecraft potential probed by the Rosetta Plasma Consortium/LAngmuir Probe on ion detection is assessed. An ionospheric model has been developed to assess the different ion density profiles and compare them to the ROSINA/DFMS measurements. It is also used to interpret the ROSINA/DFMS observations when different ion species have similar masses, and their respective densities are not high enough to disentangle them using the ROSINA/DFMS high-resolution mode. The different ion species that have been reported in the coma of 67P are summarized and compared with the ions detected at comet 1P/Halley during the Giotto mission.

  • 41.
    Heritier, K. L.
    et al.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Altwegg, K.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Berthelier, J. -J
    Beth, A.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Carr, C. M.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    De Keyser, J.
    Royal Belgian Inst Space Aeron, BIRA IASB, Ringlaan 3, Brussels, Belgium.
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Fuselier, S. A.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA;Univ Texas San Antonio, San Antonio, TX 78249 USA.
    Galand, M.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Gombosi, T. I.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA.
    Henri, P.
    CNRS, LPC2E, 3 Ave Rech Sci, F-45071 Orleans, France.
    Johansson, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Nilsson, H.
    Swedish Inst Space Phys, POB 812, S-98128 Kiruna, Sweden.
    Rubin, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Wedlund, C. Simon
    Univ Oslo, Dept Phys, Sem Saelands Vei 24Postbox 1048, N-0317 Oslo, Norway.
    Taylor, M. G. G. T.
    European Space Agcy, Estec, Keplerlaan 1, NL-2200 AG Noordwijk, Netherlands.
    Vigren, E.
    LATMOS IPSL CNRS UPMC UVSQ, F-94100 St Maur, France.
    On the origin of molecular oxygen in cometary comae2018Ingår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, artikel-id 2580Artikel i tidskrift (Övrigt vetenskapligt)
  • 42.
    Heritier, K. L.
    et al.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Galand, M.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Henri, P.
    Univ Orleans, CNRS, LPC2E, F-45100 Orleans, France.
    Johansson, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Beth, A.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Vallieres, X.
    Univ Orleans, CNRS, LPC2E, F-45100 Orleans, France.
    Altwegg, K.
    Univ Bern, Inst Phys, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Burch, J. L.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA.
    Carr, C.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Ducrot, E.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England;Univ Liege, Space Sci Technol & Astrophys Res STAR Inst, B-4000 Liege, Belgium.
    Hajra, R.
    Univ Orleans, CNRS, LPC2E, F-45100 Orleans, France.
    Rubin, M.
    Univ Bern, Inst Phys, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Plasma source and loss at comet 67P during the Rosetta mission2018Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 618, artikel-id A77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. The Rosetta spacecraft provided us with a unique opportunity to study comet 67P/Churyumov-Gerasimenko (67P) from a close perspective and over a 2-yr time period. Comet 67P is a weakly active comet. It was therefore unexpected to find an active and dynamic ionosphere where the cometary ions were largely dominant over the solar wind ions, even at large heliocentric distances. Aims. Our goal is to understand the different drivers of the cometary ionosphere and assess their variability over time and over the different conditions encountered by the comet during the Rosetta mission. Methods. We used a multi-instrument data-based ionospheric model to compute the total ion number density at the position of Rosetta. In-situ measurements from the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) and the Rosetta Plasma Consortium (RPC)-Ion and Electron Sensor (IES), together with the RPC-LAngmuir Probe instrument (LAP) were used to compute the local ion total number density. The results are compared to the electron densities measured by RPC-Mutual Impedance Probe (MIP) and RPC-LAP. Results. We were able to disentangle the physical processes responsible for the formation of the cometary ions throughout the 2-yr escort phase and we evaluated their respective magnitudes. The main processes are photo-ionization and electron-impact ionization. The latter is a significant source of ionization at large heliocentric distance (>2 au) and was predominant during the last 4 months of the mission. The ionosphere was occasionally subject to singular solar events, temporarily increasing the ambient energetic electron population. Solar photons were the main ionizer near perihelion at 1.3 au from the Sun, during summer 2015.

  • 43.
    Heritier, K. L.
    et al.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Henri, P.
    Univ Orleans, CNRS, LPC2E, F-45100 Orleans, France.
    Vallieres, X.
    Univ Orleans, CNRS, LPC2E, F-45100 Orleans, France.
    Galand, M.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Johansson, F. L.
    Swedish Inst Space Phys, Angstrom Lab, Lagerhyddsvagen 1, SE-75237 Uppsala, Sweden.
    Altwegg, K.
    Univ Bern, Inst Phys, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Behar, E.
    Swedish Inst Space Phys, POB 812, SE-98128 Kiruna, Sweden.
    Beth, A.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Broiles, T. W.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA.
    Burch, J. L.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA.
    Carr, C. M.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Cupido, E.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Nilsson, H.
    Swedish Inst Space Phys, POB 812, SE-98128 Kiruna, Sweden.
    Rubin, M.
    Univ Bern, Inst Phys, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Vigren, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Vertical structure of the near-surface expanding ionosphere of comet 67P probed by Rosetta2017Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, s. S118-S129Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The plasma environment has been measured for the first time near the surface of a comet. This unique data set has been acquired at 67P/Churyumov-Gerasimenko during ESA/Rosetta spacecraft's final descent on 2016 September 30. The heliocentric distance was 3.8 au and the comet was weakly outgassing. Electron density was continuously measured with Rosetta Plasma Consortium (RPC)-Mutual Impedance Probe (MIP) and RPC-LAngmuir Probe (LAP) during the descent from a cometocentric distance of 20 km down to the surface. Data set from both instruments have been cross-calibrated for redundancy and accuracy. To analyse this data set, we have developed a model driven by Rosetta Orbiter Spectrometer for Ion and Neutral Analysis-COmetary Pressure Sensor total neutral density. The two ionization sources considered are solar extreme ultraviolet radiation and energetic electrons. The latter are estimated from the RPC-Ion and Electron Sensor (IES) and corrected for the spacecraft potential probed by RPC-LAP. We have compared the results of the model to the electron densities measured by RPC-MIP and RPC-LAP at the location of the spacecraft. We find good agreement between observed and modelled electron densities. The energetic electrons have access to the surface of the nucleus and contribute as the main ionization source. As predicted, the measurements exhibit a peak in the ionospheric density close to the surface. The location and magnitude of the peak are estimated analytically. The measured ionospheric densities cannot be explained with a constant outflow velocity model. The use of a neutral model with an expanding outflow is critical to explain the plasma observations.

  • 44.
    Jakosky, B. M.
    et al.
    Univ Colorado, Boulder, CO 80309 USA..
    Grebowsky, J. M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Luhmann, J. G.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Connerney, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Eparvier, F.
    Univ Colorado, Boulder, CO 80309 USA..
    Ergun, R.
    Univ Colorado, Boulder, CO 80309 USA..
    Halekas, J.
    Univ Iowa, Iowa City, IA USA..
    Larson, D.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Mahaffy, P.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    McFadden, J.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Mitchell, D. F.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Schneider, N.
    Univ Colorado, Boulder, CO 80309 USA..
    Zurek, R.
    CALTECH, Jet Prop Lab, Pasadena, CA USA..
    Bougher, S.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Brain, D.
    Univ Colorado, Boulder, CO 80309 USA..
    Ma, Y. J.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Mazelle, C.
    CNRS, IRAP, Toulouse, France.;Univ Paul Sabatier, Toulouse, France..
    Andersson, L.
    Univ Colorado, Boulder, CO 80309 USA..
    Andrews, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Baird, D.
    NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA..
    Baker, D.
    Univ Colorado, Boulder, CO 80309 USA..
    Bell, J. M.
    Natl Inst Aerosp, Hampton, VA USA..
    Benna, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Chaffin, M.
    Univ Colorado, Boulder, CO 80309 USA..
    Chamberlin, P.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Chaufray, Y. -Y
    Clarke, J.
    Boston Univ, Boston, MA 02215 USA..
    Collinson, G.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Combi, M.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Crary, F.
    Univ Colorado, Boulder, CO 80309 USA..
    Cravens, T.
    Univ Kansas, Lawrence, KS 66045 USA..
    Crismani, M.
    Univ Colorado, Boulder, CO 80309 USA..
    Curry, S.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Curtis, D.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Deighan, J.
    Univ Colorado, Boulder, CO 80309 USA..
    Delory, G.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Dewey, R.
    Univ Colorado, Boulder, CO 80309 USA..
    DiBraccio, G.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Dong, C.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Dong, Y.
    Univ Colorado, Boulder, CO 80309 USA..
    Dunn, P.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Elrod, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    England, S.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Espley, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Evans, S.
    Computat Phys Inc, Boulder, CO USA..
    Fang, X.
    Univ Colorado, Boulder, CO 80309 USA..
    Fillingim, M.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Fortier, K.
    Univ Colorado, Boulder, CO 80309 USA..
    Fowler, C. M.
    Univ Colorado, Boulder, CO 80309 USA..
    Fox, J.
    Wright State Univ, Dayton, OH 45435 USA..
    Groeller, H.
    Univ Arizona, Tucson, AZ USA..
    Guzewich, S.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Hara, T.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Harada, Y.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Holsclaw, G.
    Univ Colorado, Boulder, CO 80309 USA..
    Jain, S. K.
    Univ Colorado, Boulder, CO 80309 USA..
    Jolitz, R.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Leblanc, F.
    CNRS, Lab Atmospheres Milieux & Observat Spatiales, Paris, France..
    Lee, C. O.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Lee, Y.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Lefevre, F.
    CNRS, Lab Atmospheres Milieux & Observat Spatiales, Paris, France..
    Lillis, R.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Livi, R.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Lo, D.
    Univ Arizona, Tucson, AZ USA..
    Mayyasi, M.
    Boston Univ, Boston, MA 02215 USA..
    McClintock, W.
    Univ Colorado, Boulder, CO 80309 USA..
    McEnulty, T.
    Univ Colorado, Boulder, CO 80309 USA..
    Modolo, R.
    CNRS, Lab Atmospheres Milieux & Observat Spatiales, Paris, France..
    Montmessin, F.
    CNRS, Lab Atmospheres Milieux & Observat Spatiales, Paris, France..
    Morooka, M.
    Univ Colorado, Boulder, CO 80309 USA..
    Nagy, A.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Olsen, K.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Peterson, W.
    Univ Colorado, Boulder, CO 80309 USA..
    Rahmati, A.
    Univ Kansas, Lawrence, KS 66045 USA..
    Ruhunusiri, S.
    Univ Iowa, Iowa City, IA USA..
    Russell, C. T.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Sakai, S.
    Univ Kansas, Lawrence, KS 66045 USA..
    Sauvaud, J. -A
    Seki, K.
    Nagoya Univ, Nagoya, Aichi 4648601, Japan..
    Steckiewicz, M.
    CNRS, IRAP, Toulouse, France.;Univ Paul Sabatier, Toulouse, France..
    Stevens, M.
    Naval Res Lab, Washington, DC 20375 USA..
    Stewart, A. I. F.
    Univ Colorado, Boulder, CO 80309 USA..
    Stiepen, A.
    Univ Colorado, Boulder, CO 80309 USA..
    Stone, S.
    Univ Arizona, Tucson, AZ USA..
    Tenishev, V.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Thiemann, E.
    Univ Colorado, Boulder, CO 80309 USA..
    Tolson, R.
    N Carolina State Univ, Raleigh, NC 27695 USA..
    Toublanc, D.
    CNRS, IRAP, Toulouse, France.;Univ Paul Sabatier, Toulouse, France..
    Vogt, M.
    Boston Univ, Boston, MA 02215 USA..
    Weber, T.
    Univ Colorado, Boulder, CO 80309 USA..
    Withers, P.
    Boston Univ, Boston, MA 02215 USA..
    Woods, T.
    Univ Colorado, Boulder, CO 80309 USA..
    Yelle, R.
    Univ Arizona, Tucson, AZ USA..
    MAVEN observations of the response of Mars to an interplanetary coronal mass ejection2015Ingår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 350, nr 6261, artikel-id aad0210Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ongoing ion loss to space, the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft made comprehensive measurements of the Mars upper atmosphere, ionosphere, and interactions with the Sun and solar wind during an interplanetary coronal mass ejection impact in March 2015. Responses include changes in the bow shock and magnetosheath, formation of widespread diffuse aurora, and enhancement of pick-up ions. Observations and models both show an enhancement in escape rate of ions to space during the event. Ion loss during solar events early in Mars history may have been a major contributor to the long-term evolution of the Mars atmosphere.

  • 45.
    Jakosky, B. M.
    et al.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Lin, R. P.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Grebowsky, J. M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Luhmann, J. G.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Mitchell, D. F.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Beutelschies, G.
    Lockheed Martin Corp, Littleton, CO USA..
    Priser, T.
    Lockheed Martin Corp, Littleton, CO USA..
    Acuna, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Andersson, L.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Baird, D.
    NASA, JSC, Houston, TX USA..
    Baker, D.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Bartlett, R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Benna, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Bougher, S.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Brain, D.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Carson, D.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Cauffman, S.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Chamberlin, P.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Chaufray, J. -Y
    Cheatom, O.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Clarke, J.
    Boston Univ, Boston, MA 02215 USA..
    Connerney, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Cravens, T.
    Univ Kansas, Lawrence, KS 66045 USA..
    Curtis, D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Delory, G.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Demcak, S.
    NASA, JPL, Pasadena, CA USA..
    DeWolfe, A.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Eparvier, F.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Ergun, R.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Espley, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Fang, X.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Folta, D.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Fox, J.
    Wright State Univ, Dayton, OH 45435 USA..
    Gomez-Rosa, C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Habenicht, S.
    Lockheed Martin Corp, Littleton, CO USA..
    Halekas, J.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Holsclaw, G.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Houghton, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Howard, R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Jarosz, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Jedrich, N.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Johnson, M.
    Lockheed Martin Corp, Littleton, CO USA..
    Kasprzak, W.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Kelley, M.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    King, T.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Lankton, M.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Larson, D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Leblanc, F.
    CNRS, LATMOS, Paris, France..
    Lefevre, F.
    CNRS, LATMOS, Paris, France..
    Lillis, R.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Mahaffy, P.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Mazelle, C.
    IRAP, Toulouse, France..
    McClintock, W.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    McFadden, J.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Mitchell, D. L.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Montmessin, F.
    CNRS, LATMOS, Paris, France..
    Morrissey, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Peterson, W.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Possel, W.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Sauvaud, J. -A
    Schneider, N.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Sidney, W.
    Lockheed Martin Corp, Littleton, CO USA..
    Sparacino, S.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Stewart, A. I. F.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Tolson, R.
    Natl Inst Aerosp, Hampton, VA USA..
    Toublanc, D.
    IRAP, Toulouse, France..
    Waters, C.
    Lockheed Martin Corp, Littleton, CO USA..
    Woods, T.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Yelle, R.
    Univ Arizona, Tucson, AZ USA..
    Zurek, R.
    NASA, JPL, Pasadena, CA USA..
    The Mars Atmosphere and Volatile Evolution (MAVEN) Mission2015Ingår i: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 195, nr 1-4, s. 3-48Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The MAVEN spacecraft launched in November 2013, arrived at Mars in September 2014, and completed commissioning and began its one-Earth-year primary science mission in November 2014. The orbiter's science objectives are to explore the interactions of the Sun and the solar wind with the Mars magnetosphere and upper atmosphere, to determine the structure of the upper atmosphere and ionosphere and the processes controlling it, to determine the escape rates from the upper atmosphere to space at the present epoch, and to measure properties that allow us to extrapolate these escape rates into the past to determine the total loss of atmospheric gas to space through time. These results will allow us to determine the importance of loss to space in changing the Mars climate and atmosphere through time, thereby providing important boundary conditions on the history of the habitability of Mars. The MAVEN spacecraft contains eight science instruments (with nine sensors) that measure the energy and particle input from the Sun into the Mars upper atmosphere, the response of the upper atmosphere to that input, and the resulting escape of gas to space. In addition, it contains an Electra relay that will allow it to relay commands and data between spacecraft on the surface and Earth.

  • 46.
    Johansson, Fredrik L.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Rymd- och plasmafysik.
    Paulsson, J. J. P.
    Univ Oslo, Dept Phys, Sem Saelands Vei 24,Postbox 1048, N-0317 Oslo, Norway.
    Harang, S. S.
    Univ Oslo, Dept Phys, Sem Saelands Vei 24,Postbox 1048, N-0317 Oslo, Norway.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Mannel, T.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria;Karl Franzens Univ Graz, Phys Inst, Univ Pl 5, A-8010 Graz, Austria.
    Vigren, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Edberg, Niklas J. T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Miloch, W. J.
    Univ Oslo, Dept Phys, Sem Saelands Vei 24,Postbox 1048, N-0317 Oslo, Norway.
    Wedlund, C. Simon
    Univ Oslo, Dept Phys, Sem Saelands Vei 24,Postbox 1048, N-0317 Oslo, Norway.
    Thiemann, E.
    Univ Colorado, Lab Atmospher & Space Phys, 3665 Discovery Dr, Boulder, CO 80303 USA.
    Eparvier, F.
    Univ Colorado, Lab Atmospher & Space Phys, 3665 Discovery Dr, Boulder, CO 80303 USA.
    Andersson, L.
    Univ Colorado, Lab Atmospher & Space Phys, 3665 Discovery Dr, Boulder, CO 80303 USA.
    Rosetta photoelectron emission and solar ultraviolet flux at comet 67P2017Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, s. S626-S635Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Langmuir Probe instrument on Rosetta monitored the photoelectron emission current of the probes during the Rosetta mission at comet 67P/Churyumov-Gerasimenko, in essence acting as a photodiode monitoring the solar ultraviolet radiation at wavelengths below 250 nm. We have used three methods of extracting the photoelectron saturation current from the Langmuir probe measurements. The resulting data set can be used as an index of the solar far and extreme ultraviolet at the Rosetta spacecraft position, including flares, in wavelengths which are important for photoionization of the cometary neutral gas. Comparing the photoemission current to data measurements by MAVEN/EUVM and TIMED/SEE, we find good correlation when 67P was at large heliocentric distances early and late in the mission, but up to 50 per cent decrease of the expected photoelectron current at perihelion. We discuss possible reasons for the photoemission decrease, including scattering and absorption by nanograins created by disintegration of cometary dust far away from the nucleus.

  • 47.
    Karlsson, T.
    et al.
    KTH Royal Inst Technol, Sch Elect Engn, Dept Space & Plasma Phys, Stockholm, Sweden..
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Odelstad, Elias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    André, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Dickeli, G.
    KTH Royal Inst Technol, Sch Elect Engn, Dept Space & Plasma Phys, Stockholm, Sweden..
    Kullen, A.
    KTH Royal Inst Technol, Sch Elect Engn, Dept Space & Plasma Phys, Stockholm, Sweden..
    Lindqvist, P. -A
    Nilsson, H.
    Swedish Inst Space Phys, Kiruna, Sweden..
    Richter, I.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterrestrial Phys, Braunschweig, Germany..
    Rosetta measurements of lower hybrid frequency range electric field oscillations in the plasma environment of comet 67P2017Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 44, nr 4, s. 1641-1651Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electric field measurements from cometary environments are very rare but can provide important information on how plasma waves help fashion the plasma environment. The long dwelling time of the Rosetta spacecraft close to comet 67P/Churyumov-Gerasimenko promises to improve this state. We here present the first electric field measurements from 67P, performed by the Rosetta dual Langmuir probe instrument LAP. Measurements of the electric field from cometocentric distances of 149 and 348 km are presented together with estimates of plasma density changes. Persistent wave activity around the local H2O+ lower hybrid frequency is observed, with the largest amplitudes observed at sharp plasma gradients. We demonstrate that the necessary requirements for the lower hybrid drift instability to be operating are fulfilled. We suggest that lower hybrid waves are responsible for the creation of a warm electron population, the origins of which have been unknown so far, by heating ambient electrons in the magnetic field-parallel direction.

  • 48.
    Khotyaintsev, Yuri V.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Lindqvist, P. -A
    Cully, C. M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Andre, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    In-flight calibration of double-probe DC electric field measurements on Cluster2014Ingår i: Geoscientific Instrumentation, Methods and Data Systems, ISSN 2193-0856, E-ISSN 2193-0864, Vol. 4, nr 1, s. 85-107Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Double-probe electric field instrument with long wire booms is one of the most popular techniques for in situ measurement of DC and AC electric fields in plasmas on spinning spacecraft platforms, which have been employed on a large number of space missions. Here we present an overview of the calibration procedure used for the EFW instrument on Cluster, which involves spin fits of the data and correction of several offsets. We also describe the procedure for the offset determination and present results for the long-term evolution of the offsets.

  • 49.
    Khotyaintsev, Yuri V.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Lindqvist, P. -A
    Cully, Christopher M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders I.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    André, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    In-flight calibration of double-probe electric field measurements on Cluster2014Ingår i: Geoscientific Instrumentation, Methods and Data Systems, ISSN 2193-0856, E-ISSN 2193-0864, Vol. 3, nr 2, s. 143-151Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Double-probe electric field instrument with long wire booms is one of the most popular techniques for in situ measurement of electric fields in plasmas on spinning spacecraft platforms, which have been employed on a large number of space missions. Here we present an overview of the calibration procedure used for the Electric Field and Wave (EFW) instrument on Cluster, which involves spin fits of the data and correction of several offsets. We also describe the procedure for the offset determination and present results for the long-term evolution of the offsets.

  • 50.
    Knudsen, D. J.
    et al.
    Univ Calgary, Dept Phys & Astron, Calgary, AB, Canada.
    Burchill, J. K.
    Univ Calgary, Dept Phys & Astron, Calgary, AB, Canada.
    Buchert, Stephan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Eriksson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Gill, Reine
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Wahlund, Jan-Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Åhlén, Lennart
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Smith, M.
    COM DEV Int, Cambridge, ON, Canada.
    Moffat, B.
    Univ Waterloo, Ctr Educ Math & Comp, Waterloo, ON, Canada;COM DEV Int, Cambridge, ON, Canada.
    Thermal ion imagers and Langmuir probes in the Swarm electric field instruments2017Ingår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, nr 2, s. 2655-2673Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The European Space Agency's three Swarm satellites were launched on 22 November 2013 into nearly polar, circular orbits, eventually reaching altitudes of 460 km (Swarm A and C) and 510 km (Swarm B). Swarm's multiyear mission is to make precision, multipoint measurements of low-frequency magnetic and electric fields in Earth's ionosphere for the purpose of characterizing magnetic fields generated both inside and external to the Earth, along with the electric fields and other plasma parameters associated with electric current systems in the ionosphere and magnetosphere. Electric fields perpendicular to the magnetic field.B are determined through ion drift velocity v(i) and magnetic field measurements via the relation.E. = -.vi x.B. Ion drift is derived from two-dimensional images of low-energy ion distribution functions provided by two Thermal Ion Imager (TII) sensors viewing in the horizontal and vertical planes;v(i) is corrected for spacecraft potential as determined by two Langmuir probes (LPs) which also measure plasma density ne and electron temperature T-e. The TII sensors use a microchannel-plate-intensified phosphor screen imaged by a charge-coupled device to generate high-resolution distribution images (66 x 40 pixels) at a rate of 16 s(-1). Images are partially processed on board and further on the ground to generate calibrated data products at a rate of 2 s(-1); these include.vi,.E., and ion temperature T-i in addition to electron temperature Te and plasma density n(e) from the LPs.

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