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  • 301.
    Forozesh, Kamyar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    The influence of the dispersionmap on optical OFDM transmissions2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Fiber-optic networks are an integral part of todays digital communication system. In these networks, distances of typically 400 km to 6000 km are linked together, and information is transfered at extremely high data rates. As the demands for capacity increases, finding new methods for cost effective long-haul transmission systems that can be used to increase the capacity becomes of high interest. In this work Orthogonal Frequency Division Multiplexing (OFDM), which is a standard digital modulation format in many wireless communication systems, for instance the IEEE 802.11n, is adapted to the optical domain and used for data transmission. The advantage of OFDM in the optical domain is that it transforms a high data rate stream into many simultaneously low bit rate streams that are efficiently frequency multiplexed. By doing so high spectral efficiency is achieved and many of the impairments encountered in high data rate transmissions are avoided. The disadvantage is however, that OFDM has inherently a high peak-to-average power ratio. As a result, OFDM suffers from nonlinearities occurring along the transmission line. The low nonlinear tolerance of OFDM in fiber optic applications restricts the feasible transmission distance. The goal of this work is to assess the suitability of OFDM in fiber-optic communications

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  • 302. Forsyth, C.
    et al.
    Fazakerley, A. N.
    Walsh, A. P.
    Watt, C. E. J.
    Garza, K. J.
    Owen, C. J.
    Constantinescu, D.
    Dandouras, I.
    Fornacon, K. -H
    Lucek, E.
    Marklund, G. T.
    Sadeghi, S. S.
    Khotyaintsev, Yuri
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Masson, A.
    Doss, N.
    Temporal evolution and electric potential structure of the auroral acceleration region from multispacecraft measurements2012In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, p. A12203-Article in journal (Refereed)
    Abstract [en]

    Bright aurorae can be excited by the acceleration of electrons into the atmosphere in violation of ideal magnetohydrodynamics. Modeling studies predict that the accelerating electric potential consists of electric double layers at the boundaries of an acceleration region but observations suggest that particle acceleration occurs throughout this region. Using multispacecraft observations from Cluster, we have examined two upward current regions on 14 December 2009. Our observations show that the potential difference below C4 and C3 changed by up to 1.7 kV between their respective crossings, which were separated by 150 s. The field-aligned current density observed by C3 was also larger than that observed by C4. The potential drop above C3 and C4 was approximately the same in both crossings. Using a novel technique of quantitively comparing the electron spectra measured by Cluster 1 and 3, which were separated in altitude, we determine when these spacecraft made effectively magnetically conjugate observations, and we use these conjugate observations to determine the instantaneous distribution of the potential drop in the AAR. Our observations show that an average of 15% of the potential drop in the AAR was located between C1 at 6235 km and C3 at 4685 km altitude, with a maximum potential drop between the spacecraft of 500 V, and that the majority of the potential drop was below C3. Assuming a spatial invariance along the length of the upward current region, we discuss these observations in terms of temporal changes and the vertical structure of the electrostatic potential drop and in the context of existing models and previous single- and multispacecraft observations. Citation: Forsyth, C., et al. (2012), Temporal evolution and electric potential structure of the auroral acceleration region from multispacecraft measurements, J. Geophys. Res., 117, A12203, doi: 10.1029/2012JA017655.

  • 303.
    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 University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    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 University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    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 ionosphere2015In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, no 21, p. 8854-8861Article in journal (Refereed)
    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.

  • 304.
    Fowler, C. M.
    et al.
    University of Colorado Boulder, Laboratory for Atmospheric and Space Physics.
    Andersson, L.
    University of Colorado Boulder, Laboratory for Atmospheric and Space Physics.
    Halekas, J.
    University Of Iowa, Department of Physics And Astronomy.
    Espley, J. R.
    NASA, Goddard Space Flight Center.
    Mazelle, C.
    University of Toulouse, CNRS, UPS, IRAP,CNES.
    Coughlin, E. R.
    University of California Berkeley, Department Astronomy; University of California Berkeley, Theoretical Astrophysics Center; Einstein Fellow.
    Ergun, R. E.
    University of Colorado Boulder, Laboratory for Atmospheric and Space Physics.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Connerney, J. E. P.
    NASA, Goddard Space Flight Center.
    Jakosky, B.
    University of Colorado Boulder, Laboratory for Atmospheric and Space Physics.
    Electric and magnetic variations in the near-Mars environment2017In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 8, p. 8536-8559Article in journal (Refereed)
    Abstract [en]

    For the first time at Mars the statistical distribution of (1-D) electric field wave power in the magnetosphere is presented, along with the distribution of magnetic field wave power, as observed by the Mars Atmosphere and Volatile EvolutioN spacecraft from the first 14.5months of the mission. Wave power in several different frequency bands was investigated, and the strongest wave powers were observed at the lowest frequencies. The presented statistical studies suggest that the full thermalization of ions within the magnetosheath does not appear to occur, as has been predicted by previous studies. Manual inspection of 140 periapsis passes on the dayside shows that Poynting fluxes (at 2-16 Hz) between similar to 10(-11) and 10(-8) Wm(-2) reach the upper ionosphere for all 140 cases. Wave power is not observed in the ionosphere for integrated electron densities greater than 10(10.8)cm(-2), corresponding to typical depths of 100-200 km. The observations presented support previous suggestions that energy from the Mars-solar wind interaction can propagate into the upper ionosphere and may provide an ionospheric heating source. Upstream of the shock, the orientation of the solar wind interplanetary magnetic field was shown to significantly affect the statistical distribution of wave power, based on whether the spacecraft was likely magnetically connected to the shock or not-something that is predicted but has not been quantitatively shown at Mars before. In flight performance and caveats of the Langmuir Probe and Waves electric field power spectra are also discussed.

  • 305.
    Fraternale, Federico
    et al.
    Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA..
    Zhao, Lingling
    Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA..
    Pogorelov, Nikolai V. V.
    Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA.;Univ Alabama, Dept Space Sci, Huntsville, AL USA..
    Sorriso-Valvo, Luca
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Swedish Inst Space Phys IRF, Angstrom Lab, Uppsala, Sweden.;CNR, Ist Sci & Tecnol Plasmi, Bari, Italy..
    Redfield, Seth
    Wesleyan Univ, Dept Astron, Middletown, CT USA.;Wesleyan Univ, Van Vleck Observ, Middletown, CT USA..
    Zhang, Ming
    Florida Inst Technol, Dept Phys & Space Sci, Melbourne, FL USA..
    Ghanbari, Keyvan
    Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA..
    Florinski, Vladimir
    Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA.;Univ Alabama, Dept Space Sci, Huntsville, AL USA..
    Chen, Thomas Y. Y.
    Columbia Univ, New York, NY USA..
    Exploring turbulence from the Sun to the local interstellar medium: Current challenges and perspectives for future space missions2022In: Frontiers in Astronomy and Space Sciences, E-ISSN 2296-987X, Vol. 9Article, review/survey (Refereed)
    Abstract [en]

    Turbulence is ubiquitous in space plasmas. It is one of the most important subjects in heliospheric physics, as it plays a fundamental role in the solar wind-local interstellar medium interaction and in controlling energetic particle transport and acceleration processes. Understanding the properties of turbulence in various regions of the heliosphere with vastly different conditions can lead to answers to many unsolved questions opened up by observations of the magnetic field, plasma, pickup ions, energetic particles, radio and UV emissions, and so on. Several space missions have helped us gain preliminary knowledge on turbulence in the outer heliosphere and the very local interstellar medium. Among the past few missions, the Voyagers have paved the way for such investigations. This paper summarizes the open challenges and voices our support for the development of future missions dedicated to the study of turbulence throughout the heliosphere and beyond.

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    FULLTEXT01
  • 306.
    Fränz, M.
    et al.
    Max Planck Inst Sonnensyst Forsch, D-37077 Gottingen, Germany..
    Dubinin, E.
    Max Planck Inst Sonnensyst Forsch, D-37077 Gottingen, Germany..
    Andrews, David
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Barabash, S.
    Swedish Inst Space Phys, S-89128 Kiruna, Sweden..
    Nilsson, H.
    Swedish Inst Space Phys, S-89128 Kiruna, Sweden..
    Fedorov, A.
    Ctr Etud Spatiale Rayonnements, F-31028 Toulouse, France..
    Cold ion escape from the Martian ionosphere2015In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 119, p. 92-102Article in journal (Refereed)
    Abstract [en]

    We here report on new measurements of the escape flux of oxygen ions from Mars by combining the observations of the ASPERA-3 and MARSIS experiments on board the European Mars Express spacecraft. We show that in previous estimates of the total heavy ion escape flow the contribution of the cold ionospheric outflow with energies below 10 eV has been underestimated. Both case studies and the derived flow pattern indicate that the cold plasma observed by MARSIS and the superthermal plasma observed by ASPERA-3 move with the same bulk speed in most regions of the Martian tail. We determine maps of the tailside heavy ion flux distribution derived from mean ion velocity distributions sampled over 7 years. If we assume that the superthermal bulk speed derived from these long time averages of the ion distribution function represent the total plasma bulk speed we derive the total tailside plasma flux. Assuming cylindrical symmetry we determine the mean total escape rate for the years 2007-2014 at 2.8 +/- 0.4 x 10(25) atoms/s which is in good agreement with model estimates. A possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside.

  • 307.
    Fu, H. S.
    et al.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Cao, J. B.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Cao, D.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Wang, Z.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA.
    Huang, S. Y.
    Wuhan Univ, Sch Elect & Informat, Wuhan, Hubei, Peoples R China.
    Evidence of Magnetic Nulls in Electron Diffusion Region2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 1, p. 48-54Article in journal (Refereed)
    Abstract [en]

    Theoretically, magnetic reconnection—the process responsible for solar flares and magnetospheric substorms—occurs at the X‐line or radial null in the electron diffusion region (EDR). However, whether this theory is correct is unknown, because the radial null (X‐line) has never been observed inside the EDR due to the lack of efficient techniques and the scarcity of EDR measurements. Here we report such evidence, using data from the recent MMS mission and the newly developed First‐Order Taylor Expansion (FOTE) Expansion technique. We investigate 12 EDR candidates at the Earth's magnetopause and find radial nulls (X‐lines) in all of them. In some events, spacecraft are only 3 km (one electron inertial length) away from the null. We reconstruct the magnetic topology of these nulls and find it agrees well with theoretical models. These nulls, as reconstructed for the first time inside the EDR by the FOTE technique, indicate that the EDR is active and the reconnection process is ongoing.

    Plain Language Summary: Magnetic reconnection is a key process responsible for many explosive phenomena in nature such as solar flares and magnetospheric substorms. Theoretically, such process occurs at the X‐line or radial null in the electron diffusion region (EDR). However, whether this theory is correct is still unknown, because the radial null (X‐line) has never been observed inside the EDR due to the lack of efficient technique and the scarcity of EDR measurements. Here we report such evidence, using data from the recent MMS mission and the newly developed FOTE technique.

  • 308. Fu, H. S.
    et al.
    Cao, J. B.
    Cully, C. M.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Angelopoulos, V.
    Zong, Q. -G
    Santolik, O.
    Macusova, E.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Liu, W. L.
    Lu, H. Y.
    Zhou, M.
    Huang, S. Y.
    Zhima, Z.
    Whistler-mode waves inside flux pileup region: Structured or unstructured?2014In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 119, no 11, p. 9089-9100Article in journal (Refereed)
    Abstract [en]

    During reconnection, a flux pileup region (FPR) is formed behind a dipolarization front in an outflow jet. Inside the FPR, the magnetic field magnitude and Bz component increase and the whistler-mode waves are observed frequently. As the FPR convects toward the Earth during substorms, it is obstructed by the dipolar geomagnetic field to form a near-Earth FPR. Unlike the structureless emissions inside the tail FPR, we find that the whistler-mode waves inside the near-Earth FPR can exhibit a discrete structure similar to chorus. Both upper band and lower band chorus are observed, with the upper band having a larger propagation angle (and smaller wave amplitude) than the lower band. Most chorus elements we observed are rising-tone type, but some are falling-tone type. We notice that the rising-tone chorus can evolve into falling-tone chorus within <3s. One of the factors that may explain why the waves are unstructured inside the tail FPR but become discrete inside the near-Earth FPR is the spatial inhomogeneity of magnetic field: we find that such inhomogeneity is small inside the near-Earth FPR but large inside the tail FPR.

  • 309.
    Fu, H. S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cao, J. B.
    Khotyaintsev, Yu. V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Sitnov, M. I.
    Runov, A.
    Fu, S. Y.
    Hamrin, M.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Retino, A.
    Ma, Y. D.
    Lu, H. Y.
    Wei, X. H.
    Huang, S. Y.
    Dipolarization fronts as a consequence of transient reconnection: In situ evidence2013In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, no 23, p. 6023-6027Article in journal (Refereed)
    Abstract [en]

    Dipolarization fronts (DFs) are frequently detected in the Earth's magnetotail from XGSM = −30 RE to XGSM = −7 RE. How these DFs are formed is still poorly understood. Three possible mechanisms have been suggested in previous simulations: (1) jet braking, (2) transient reconnection, and (3) spontaneous formation. Among these three mechanisms, the first has been verified by using spacecraft observation, while the second and third have not. In this study, we show Cluster observation of DFs inside reconnection diffusion region. This observation provides in situ evidence of the second mechanism: Transient reconnection can produce DFs. We suggest that the DFs detected in the near-Earth region (XGSM > −10 RE) are primarily attributed to jet braking, while the DFs detected in the mid- or far-tail region (XGSM < −15 RE) are primarily attributed to transient reconnection or spontaneous formation. In the jet-braking mechanism, the high-speed flow “pushes” the preexisting plasmas to produce the DF so that there is causality between high-speed flow and DF. In the transient-reconnection mechanism, there is no causality between high-speed flow and DF, because the frozen-in condition is violated.

  • 310.
    Fu, H. S.
    et al.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China..
    Cao, J. B.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China..
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Andre, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dunlop, M.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China..
    Liu, W. L.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China..
    Lu, H. Y.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China..
    Huang, S. Y.
    Wuhan Univ, Sch Elect & Informat, Wuhan 430072, Peoples R China..
    Ma, Y. D.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China..
    Eriksson, Elin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Identifying magnetic reconnection events using the FOTE method2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 2, p. 1263-1272Article in journal (Refereed)
    Abstract [en]

    A magnetic reconnection event detected by Cluster is analyzed using three methods: Single-spacecraft Inference based on Flow-reversal Sequence (SIFS), Multispacecraft Inference based on Timing a Structure (MITS), and the First-Order Taylor Expansion (FOTE). Using the SIFS method, we find that the reconnection structure is an X line; while using the MITS and FOTE methods, we find it is a magnetic island (O line). We compare the efficiency and accuracy of these three methods and find that the most efficient and accurate approach to identify a reconnection event is FOTE. In both the guide and nonguide field reconnection regimes, the FOTE method is equally applicable. This study for the first time demonstrates the capability of FOTE in identifying magnetic reconnection events; it would be useful to the forthcoming Magnetospheric Multiscale (MMS) mission. ion

  • 311. Fu, H. S.
    et al.
    Cao, J. B.
    Zhima, Z.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Angelopoulos, V.
    Santolik, O.
    Omura, Y.
    Taubenschuss, Ulrich
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Chen, L.
    Huang, S. Y.
    First observation of rising-tone magnetosonic waves2014In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 41, no 21, p. 7419-7426Article in journal (Refereed)
    Abstract [en]

    Magnetosonic (MS) waves are linearly polarized emissions confined near the magnetic equator with wave normal angle near 90 degrees and frequency below the lower hybrid frequency. Such waves, also termed equatorial noise, were traditionally known to be "temporally continuous" in their time-frequency spectrogram. Here we show for the first time that MS waves actually have discrete wave elements with rising-tone features in their spectrogram. The frequency sweep rate of MS waves, similar to 1 Hz/s, is between that of chorus and electromagnetic ion cyclotron (EMIC) waves. For the two events we analyzed, MS waves occur outside the plasmapause and cannot penetrate into the plasmasphere; their power is smaller than that of chorus. We suggest that the rising-tone feature of MS waves is a consequence of nonlinear wave-particle interaction, as is the case with chorus and EMIC waves.

  • 312.
    Fu, H. S.
    et al.
    Beihang Univ, Sch Astronaut, Space Sci Inst, Beijing 100191, Peoples R China..
    Cao, J. B.
    Beihang Univ, Sch Astronaut, Space Sci Inst, Beijing 100191, Peoples R China..
    Zhima, Z.
    Beihang Univ, Sch Astronaut, Space Sci Inst, Beijing 100191, Peoples R China..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Santolik, O.
    Inst Atmospher Phys ASCR, Prague, Czech Republic.;Charles Univ Prague, Fac Math & Phys, Prague, Czech Republic..
    Taubenschuss, Ulrich
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Discrete magnetosonic waves as an evidence of nonlinear wave-particle interaction2014In: 2014 XXXITH URSI General Assembly And Scientific Symposium (URSI GASS): General Assembly And Scientific Symposium, 2014Conference paper (Refereed)
    Abstract [en]

    Two events, showing strong emissions near the lower hybrid frequency, are studied in detail in this paper. By analyzing the polarization degree, wave normal angle, and ellipticity, we conclude that the emissions are magnetosonic (MS) waves. These MS waves have opposite poynting fluxes in the radial and azimuthal direction, indicating that they were detected near the source region. In the wave spectrogram, discrete and "rising-tone" elements are found, suggesting that MS waves probably are a consequence of nonlinear wave-particle interaction.

  • 313.
    Fu, H. S.
    et al.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China.
    Chen, F.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China.
    Chen, Z. Z.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China.
    Xu, Y.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China.
    Wang, Z.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China.
    Liu, Y. Y.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China.
    Liu, C. M.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ergun, R. E.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80303 USA.
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Code 916, Greenbelt, MD 20771 USA.
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78228 USA.
    First Measurements of Electrons and Waves inside an Electrostatic Solitary Wave2020In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 124, no 9, article id 095101Article in journal (Refereed)
    Abstract [en]

    Electrostatic solitary wave (ESW)-a Debye-scale structure in space plasmas-was believed to accelerate electrons. However, such a belief is still unverified in spacecraft observations, because the ESW usually moves fast in spacecraft frame and its interior has never been directly explored. Here, we report the first measurements of an ESW's interior, by the Magnetospheric Multiscale mission located in a magnetotail reconnection jet. We find that this ESW has a parallel scale of 5 lambda(De) (Debye length), a superslow speed (99 km/s) in spacecraft frame, a longtime duration (250 ms), and a potential drop e phi(0)/kT(e) similar to 5%. Inside the ESW, surprisingly, there is no electron acceleration, no clear change of electron distribution functions, but there exist strong electrostatic electron cyclotron waves. Our observations challenge the conventional belief that ESWs are efficient at particle acceleration.

  • 314.
    Fu, H. S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Y. V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Andre, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Sergeev, V. A.
    Huang, S. Y.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Kronberg, E. A.
    Daly, P. W.
    Pitch angle distribution of suprathermal electrons behind dipolarization fronts: A statistical overview2012In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, p. A12221-Article in journal (Refereed)
    Abstract [en]

    We examine the pitch angle distribution (PAD) of suprathermal electrons (> 40 keV) inside the flux pileup regions (FPRs) that are located behind the dipolarization fronts (DFs), in order to better understand the particle energization mechanisms operating therein. The 303 earthward-propagating DFs observed during 9 years (2001-2009) by Cluster 1 have been analyzed and divided into two groups according to the differential fluxes of the > 40 keV electrons inside the FPR. One group, characterized by the low flux (F < 500/cm(2) , s . sr . keV), consists of 153 events and corresponds to a broad distribution of IMF Bz components. The other group, characterized by the high flux (F >= 500/cm(2) . s . sr . keV), consists of 150 events and corresponds to southward IMF Bz components. Only the high-flux group is considered to investigate the PAD of the > 40 keV electrons as the low-flux situation may lead to large uncertainties in computing the anisotropy factor that is defined as A = F-perpendicular to/F-parallel to - 1 for F-perpendicular to > F-parallel to, and A = -F-parallel to/F-perpendicular to + 1 for F-perpendicular to < F-parallel to. We find that, among the 150 events, 46 events have isotropic distribution (vertical bar A vertical bar <= 0.5); 60 events have perpendicular distribution (A > 0.5), and 44 events have field-aligned distribution inside the FPR (A < -0.5). The perpendicular distribution appears mainly inside the growing FPR, where the flow velocity is increasing and the local flux tube is compressed. The field-aligned distribution occurs mainly inside the decaying FPR, where the flow velocity is decreasing and the local flux tube is expanding. Inside the steady FPR, we observed primarily the isotropic distribution of suprathermal electrons. This statistical result confirms the previous case study and gives an overview of the PAD of suprathermal electrons behind DFs.

  • 315.
    Fu, H. S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Retino, A.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Energetic electron acceleration by unsteady magnetic reconnection2013In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 9, no 7, p. 426-430Article in journal (Refereed)
    Abstract [en]

    The mechanism that produces energetic electrons during magnetic reconnection is poorly understood. This is a fundamental process responsible for stellar flares(1,2),substorms(34), and disruptions in fusion experiments(5,6).Observations in the solar chromosphere(1) and the Earth's magnetosphere(7-10) indicate significant electron acceleration during reconnection, whereas in the solar wind, energetic electrons are absent(11). Here we show that energetic electron acceleration is caused by unsteady reconnection. In the Earth's magnetosphere and the solar chromosphere, reconnection is unsteady, so energetic electrons are produced; in the solar wind, reconnection is steady(12), so energetic electrons are absent(11). The acceleration mechanism is quasi-adiabatic: betatron and Fermi acceleration in outflow jets are two processes contributing to electron energization during unsteady reconnection. The localized betatron acceleration in the outflow is responsible for at least half of the energy gain for the peak observed fluxes.

  • 316.
    Fu, H. S.
    et al.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China..
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cao, J. B.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China..
    Olshevsky, V.
    Katholieke Univ Leuven, Ctr Math Plasma Astrophys, Leuven, Belgium..
    Eastwood, J. P.
    Imperial Coll London, Blackett Lab, London, England..
    Retino, A.
    UPMC, Ecole Polytech, CNRS, Lab Phys Plasmas, Palaiseau, France..
    Intermittent energy dissipation by turbulent reconnection2017In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 44, no 1, p. 37-43Article in journal (Refereed)
    Abstract [en]

    Magnetic reconnectionthe process responsible for many explosive phenomena in both nature and laboratoryis efficient at dissipating magnetic energy into particle energy. To date, exactly how this dissipation happens remains unclear, owing to the scarcity of multipoint measurements of the diffusion region at the sub-ion scale. Here we report such a measurement by Clusterfour spacecraft with separation of 1/5 ion scale. We discover numerous current filaments and magnetic nulls inside the diffusion region of magnetic reconnection, with the strongest currents appearing at spiral nulls (O-lines) and the separatrices. Inside each current filament, kinetic-scale turbulence is significantly increased and the energy dissipation, Ej, is 100 times larger than the typical value. At the jet reversal point, where radial nulls (X-lines) are detected, the current, turbulence, and energy dissipations are surprisingly small. All these features clearly demonstrate that energy dissipation in magnetic reconnection occurs at O-lines but not X-lines.

  • 317.
    Fu, H. S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Beihang Univ, Space Sci Inst, Sch Astronaut, Beijing 100191, Peoples R China.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Olshevsky, V.
    Katholieke Univ Leuven, Ctr Math Plasma Astrophys, Dept Math, Leuven, Belgium.;Main Astron Observ NAS, Kiev, Ukraine..
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Cao, J. B.
    Beihang Univ, Space Sci Inst, Sch Astronaut, Beijing 100191, Peoples R China..
    Huang, S. Y.
    Ecole Polytech, CNRS, UPMC, Lab Phys Plasmas, F-91128 Palaiseau, France.;Wuhan Univ, Sch Elect & Informat, Wuhan 430072, Peoples R China.
    Retino, A.
    Ecole Polytech, CNRS, UPMC, Lab Phys Plasmas, F-91128 Palaiseau, France..
    Lapenta, G.
    Katholieke Univ Leuven, Ctr Math Plasma Astrophys, Dept Math, Leuven, Belgium..
    How to find magnetic nulls and reconstruct field topology with MMS data?2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 5, p. 3758-3782Article in journal (Refereed)
    Abstract [en]

    In this study, we apply a new method-the first-order Taylor expansion (FOTE)-to find magnetic nulls and reconstruct magnetic field topology, in order to use it with the data from the forthcoming MMS mission. We compare this method with the previously used Poincare index (PI), and find that they are generally consistent, except that the PI method can only find a null inside the spacecraft (SC) tetrahedron, while the FOTE method can find a null both inside and outside the tetrahedron and also deduce its drift velocity. In addition, the FOTE method can (1) avoid limitations of the PI method such as data resolution, instrument uncertainty (Bz offset), and SC separation; (2) identify 3-D null types (A, B, As, and Bs) and determine whether these types can degenerate into 2-D (X and O); (3) reconstruct the magnetic field topology. We quantitatively test the accuracy of FOTE in positioning magnetic nulls and reconstructing field topology by using the data from 3-D kinetic simulations. The influences of SC separation (0.05 similar to 1 d(i)) and null-SC distance (0 similar to 1 d(i)) on the accuracy are both considered. We find that (1) for an isolated null, the method is accurate when the SC separation is smaller than 1 d(i), and the null-SC distance is smaller than 0.25 similar to 0.5 d(i); (2) for a null pair, the accuracy is same as in the isolated-null situation, except at the separator line, where the field is nonlinear. We define a parameter xi vertical bar(lambda(1) +lambda(2) +lambda(3))vertical bar/vertical bar lambda vertical bar(max) in terms of the eigenvalues (lambda(i)) of the null to quantify the quality of our method-the smaller this parameter the better the results. Comparing to the previously used parameter (eta vertical bar del center dot B vertical bar/vertical bar del x B vertical bar), xi is more relevant for null identification. Using the new method, we reconstruct the magnetic field topology around a radial-type null and a spiral-type null, and find that the topologies are well consistent with those predicted in theory. We therefore suggest using this method to find magnetic nulls and reconstruct field topology with four-point measurements, particularly from Cluster and the forthcoming MMS mission. For the MMS mission, this null-finding algorithm can be used to trigger its burst-mode measurements.

  • 318.
    Fu, H. S.
    et al.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Xu, Y.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Super-efficient Electron Acceleration by an Isolated Magnetic Reconnection2019In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 870, no 2, article id L22Article in journal (Refereed)
    Abstract [en]

    Magnetic reconnection-the process typically lasting for a few seconds in space-is able to accelerate electrons. However, the efficiency of the acceleration during such a short period is still a puzzle. Previous analyses, based on spacecraft measurements in the Earth's magnetotail, indicate that magnetic reconnection can enhance electron fluxes up to 100 times. This efficiency is very low, creating an impression that magnetic reconnection is not good at particle acceleration. By analyzing Cluster data, we report here a remarkable magnetic reconnection event during which electron fluxes are enhanced by 10,000 times. Such acceleration, 100 times more efficient than those in previous studies, is caused by the betatron mechanism. Both reconnection fronts and magnetic islands contribute to the acceleration, with the former being more prominent.

  • 319.
    Fu, Huishan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cao, J. B.
    Mozer, F. S.
    Lu, H. Y.
    Yang, B.
    Chorus intensification in response to interplanetary shock2012In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, p. A01203-Article in journal (Refereed)
    Abstract [en]

    On 3 September 2009, the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites observed a significant intensification of chorus in response to the interplanetary shock in the Earth's dayside plasma trough. We analyze the wave-particle interaction and reveal that the chorus intensification can be caused by the gyroresonance between the chorus and the energetic electrons. When the electrons are scattered from resonance points to low-density regions along the diffusion curves, a part of their energy can be lost and then transferred to amplify the chorus. During the compression of the magnetosphere, the temperature anisotropy of electrons is enhanced. This makes the electron diffusion and chorus intensification very effective. The maximum growth rate after the shock is about 50% greater than that before the shock. The lower-energy (15-25 keV) electrons contribute more to the growth of chorus due to the larger density gradient along the diffusion curve. The < 10 keV electrons are almost isotropic, so they contribute little to the amplification of chorus. We investigate the free energy for the chorus intensification and find that it can be generated through the local betatron acceleration and radial diffusion processes. The local betatron acceleration results from the shock-induced compression of the magnetosphere. The linear and nonlinear growth rates are also compared. We find that the linear diffusion process works well for the present case.

  • 320.
    Fu, Huishan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cao, J. B.
    Yang, B.
    Lu, H. Y.
    Electron loss and acceleration during storm time: The contribution of wave-particle interaction, radial diffusion, and transport processes2011In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 116, p. A10210-Article in journal (Refereed)
    Abstract [en]

    During the period 19-22 November 2007, the near-equatorial satellites THEMIS D (ThD) and E (ThE) traversed the Earth's morningside magnetosphere once per day and for nearly 2 h the orbits tracked close to each other, providing an excellent opportunity to investigate the evolution of energetic electrons fluxes (EEFs) on two time scales. By analyzing the electrons in the energy range 100-300 keV, we have found that the EEFs undergo different evolutions in the different subregions of Earth's morningside magnetosphere during a moderate storm. The evolutions at three specific locations, showing, respectively, the features of electron loss, acceleration, and conservation, have been analyzed in detail. Our observations reveal that, during storm time, the evolution of EEFs involves five processes: (1) the resonant interaction between chorus and energetic electrons, which can contribute to both loss and acceleration of electrons depending on the distribution of phase space density, (2) the radial diffusion, which is indicated by the good coherence between ULF waves and EEFs and dominates in the region where the chorus is relatively weak; (3) the adiabatic transport, which affects the EEFs at L > 6 during the recovery phase and prefers to work on large time scale (>1 d); (4) the magnetopause shadowing, which can evacuate electrons at L > 7 during the storm main phase but play minor roles during the recovery phase, when the magnetopause was moving outward; (5) the magnetospheric convection, which can significantly affect the dynamics of the <100 keV but not the >100 keV electrons. All these five processes couple to each other and determine the EEFs together.

  • 321.
    Fu, Huishan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cao, J. B.
    Zong, Q-G
    Lu, H. Y.
    Huang, S. Y.
    Wei, X. H.
    Ma, Y. D.
    The role of electrons during chorus intensification: Energy source and energy loss2012In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 80, p. 37-47Article in journal (Refereed)
    Abstract [en]

    The role of electrons during the shock-induced chorus intensification observed by THEMIS D on 19 November 2007 is investigated in detail. First, the electrons are accelerated through the local betatron acceleration and radial diffusion, which are primarily in the perpendicular direction and result in the positive anisotropy (T-perpendicular to > T-//) of electrons; then they are scattered through the pitch-angle diffusion, during which the electron energies are partially transferred to amplify the chorus. In the case of interest, the energy loss is more efficient for the lower-energy (15 key) electrons because they have larger density gradient along the diffusion curves. The energetic electrons act as the intermediate in this scenario. They transfer the energies carried by the interplanetary shock to the chorus. The energetic electrons injected from magnetotail are not observed; they have no contributions to the energy source in this event.

  • 322.
    Fu, Huishan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Huang, S. Y.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Occurrence rate of earthward-propagating dipolarization fronts2012In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 39, p. L10101-Article in journal (Refereed)
    Abstract [en]

    The occurrence rate of earthward-propagating dipolarization fronts (DFs) is investigated in this paper based on the 9 years (2001-2009) of Cluster 1 data. For the first time, we select the DF events by fitting the characteristic increase in B-z using a hyperbolic tangent function. 303 earthward-propagating DFs are found; they have on average a duration of 4 s and a B-z increase of 8 nT. DFs have the maximum occurrence at Z(GSM) approximate to 0 and r approximate to 15 R-E with one event occurring every 3.9 hours, where r is the distance to the center of the Earth in the XYGSM plane. The maximum occurrence rate at Z(GSM) approximate to 0 can be explained by the steep and large increase of B-z near the central current sheet, which is consistent with previous simulations. Along the r direction, the occurrence rate increases gradually from r approximate to 20 to r approximate to 15 R-E but decreases rapidly from r approximate to 15 to r approximate to 10 R-E. This may be due to the increasing pileup of the magnetic flux from r approximate to 20 to r approximate to 15 R-E and the strong background magnetic field at r <similar to 13 R-E, where the magnetic field changes from the tail-like to dipolar shape. The maximum occurrence rate of DFs (one event per 3.9 hours) is comparable to that of substorms, indicating a relation between the two.

  • 323.
    Fu, Huishan S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Fermi and betatron acceleration of suprathermal electrons behind dipolarization fronts2011In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 38, p. L16104-Article in journal (Refereed)
    Abstract [en]

    Two dipolarization front (DF) structures observed by Cluster in the Earth midtail region (X(GSM) approximate to -15 R(E)), showing respectively the feature of Fermi and betatron acceleration of suprathermal electrons, are studied in detail in this paper. Our results show that Fermi acceleration dominates inside a decaying flux pileup region (FPR), while betatron acceleration dominates inside a growing FPR. Both decaying and growing FPRs are associated with the DF and can be distinguished by examining whether the peak of the bursty bulk flow (BBF) is co-located with the DF (decaying) or is behind the DF (growing). Fermi acceleration is routinely caused by the shrinking length of flux tubes, while betatron acceleration is caused by a local compression of the magnetic field. With a simple model, we reproduce the processes of Fermi and betatron acceleration for the higher-energy (>40 keV) electrons. For the lower-energy (<20 keV) electrons, Fermi and betatron acceleration are not the dominant processes. Our observations reveal that betatron acceleration can be prominent in the midtail region even though the magnetic field lines are significantly stretched there.

  • 324.
    Fu, Huishan S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Huang, S. Y.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Electric structure of dipolarization front at sub-proton scale2012In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 39, p. L06105-Article in journal (Refereed)
    Abstract [en]

    Using Cluster data, we investigate the electric structure of a dipolarization front (DF) - the ion inertial length (c/omega(pi)) scale boundary in the Earth's magnetotail formed at the front edge of an earthward propagating flow with reconnected magnetic flux. We estimate the current density and the electron pressure gradient throughout the DF by both single-spacecraft and multi-spacecraft methods. Comparison of the results from the two methods shows that the single-spacecraft analysis, which is capable of resolving the detailed structure of the boundary, can be applied for the DF we study. Based on this, we use the current density and the electron pressure gradient from the single-spacecraft method to investigate which terms in the generalized Ohm's law balance the electric field throughout the DF. We find that there is an electric field at ion inertia scale directed normal to the DF; it has a duskward component at the dusk flank of DF but a dawnward component at the dawn flank of DF. This electric field is balanced by the Hall (j x B/ne) and electron pressure gradient (del P-e/ne) terms at the DF, with the Hall term being dominant. Outside the narrow DF region, however, the electric field is balanced by the convection (V-i x B) term, meaning the frozen-in condition for ions is broken only at the DF itself. In the reference frame moving with the DF the tangential electric field is almost zero, indicating there is no flow of plasma across the DF and that the DF is a tangential discontinuity. The normal electric field at the DF constitutes a potential drop of similar to 1 keV, which may reflect and accelerate the surrounding ions. 

  • 325.
    Fuselier, S. A.
    et al.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78228 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    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.
    LATMOS, 4 Ave Neptune, F-94100 St Maur, France..
    Beth, A.
    Imperial Coll London, Dept Phys, Space & Atmospher Phys Grp, Prince Consort Rd, London SW7 2AZ, England..
    Bieler, A.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland.;Univ Michigan, Dept Atmospher Ocean & Space Sci, 2455 Hayward, Ann Arbor, MI 48109 USA..
    Briois, C.
    Univ Orleans, CNRS, Lab Phys & Chim Environm & Espace LPC2E, UMR 6115, F-45071 Orleans, France..
    Broiles, T. W.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78228 USA..
    Burch, J. L.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78228 USA..
    Calmonte, U.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Cessateur, G.
    Belgian Inst Space Aeron BIRA IASB, Ringlaan 3, B-1180 Brussels, Belgium..
    Combi, M.
    Imperial Coll London, Dept Phys, Space & Atmospher Phys Grp, Prince Consort Rd, London SW7 2AZ, England..
    De Keyser, J.
    Belgian Inst Space Aeron BIRA IASB, Ringlaan 3, B-1180 Brussels, Belgium..
    Fiethe, B.
    TU Braunschweig, Inst Comp & Network Engn IDA, Hans Sommer Str 66, D-38106 Braunschweig, Germany..
    Galand, M.
    Imperial Coll London, Dept Phys, Space & Atmospher Phys Grp, 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, 2455 Hayward, Ann Arbor, MI 48109 USA..
    Gunell, H.
    Belgian Inst Space Aeron BIRA IASB, Ringlaan 3, B-1180 Brussels, Belgium..
    Hansen, K. C.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, 2455 Hayward, Ann Arbor, MI 48109 USA..
    Hassig, M.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78228 USA..
    Heritier, K. L.
    Imperial Coll London, Dept Phys, Space & Atmospher Phys Grp, Prince Consort Rd, London SW7 2AZ, England..
    Korth, A.
    Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany..
    Le Roy, L.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Luspay-Kuti, A.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78228 USA..
    Mall, U.
    Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany..
    Mandt, K. E.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78228 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Petrinec, S. M.
    Lockheed Martin Adv Technol Ctr, Palo Alto, CA 94304 USA..
    Reme, H.
    Univ Toulouse, UPS OMP, IRAP, F-31400 Toulouse, France.;CNRS, IRAP, 9 Ave Colonel Roche,BP 44346, F-31028 Toulouse 4, France..
    Rinaldi, M.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78228 USA..
    Rubin, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Semon, T.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Trattner, K. J.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA..
    Tzou, C. -Y
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Waite, J. H.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78228 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Wurz, P.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Ion chemistry in the coma of comet 67P near perihelion2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, p. S67-S77Article in journal (Refereed)
    Abstract [en]

    The coma and the comet-solar wind interaction of comet 67P/Churyumov-Gerasimenko changed dramatically from the initial Rosetta spacecraft encounter in 2014 August through perihelion in 2015 August. Just before equinox (at 1.6 au from the Sun), the solar wind signal disappeared and two regions of different cometary ion characteristics were observed. These 'outer' and 'inner' regions have cometary ion characteristics similar to outside and inside the ion pileup region observed during the Giotto approach to comet 1P/Halley. Rosetta/Double-Focusing Mass Spectrometer ion mass spectrometer observations are used here to investigate the H3O+/H2O+ ratio in the outer and inner regions at 67P/Churyumov-Gerasimenko. The H3O+/H2O+ ratio and the H3O+ signal are observed to increase in the transition from the outer to the inner region and the H3O+ signal appears to be weakly correlated with cometary ion energy. These ion composition changes are similar to the ones observed during the 1P/Halley flyby. Modelling is used to determine the importance of neutral composition and transport of neutrals and ions away from the nucleus. This modelling demonstrates that changes in the H3O+/H2O+ ratio appear to be driven largely by transport properties and only weakly by neutral composition in the coma.

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  • 326.
    Fuselier, S. A.
    et al.
    SW Res Inst, Div Space Sci, San Antonio, TX 78228 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Altwegg, K.
    Univ Bern, Inst Phys, CH-3012 Bern, Switzerland..
    Balsiger, H.
    Univ Bern, Inst Phys, CH-3012 Bern, Switzerland..
    Berthelier, J. J.
    LATMOS, F-94100 St Maur, France..
    Bieler, A.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA..
    Briois, C.
    Univ Orleans, CNRS, UMR 6115, Lab Phys & Chim Environm & Espace LPC2E, F-45071 Orleans 2, France..
    Broiles, T. W.
    SW Res Inst, Div Space Sci, San Antonio, TX 78228 USA..
    Burch, J. L.
    SW Res Inst, Div Space Sci, San Antonio, TX 78228 USA..
    Calmonte, U.
    Univ Bern, Inst Phys, CH-3012 Bern, Switzerland..
    Cessateur, G.
    Belgian Inst Space Aeron BIRA IASB, B-1180 Brussels, Belgium..
    Combi, M.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA..
    De Keyser, J.
    Belgian Inst Space Aeron BIRA IASB, B-1180 Brussels, Belgium..
    Fiethe, B.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Comp & Network Engn IDA, D-38106 Braunschweig, Germany..
    Galand, M.
    Univ London Imperial Coll Sci Technol & Med, Dept Phys, Space & Atmospher Phys Grp, London SW7 2AZ, England..
    Gasc, S.
    Univ Bern, Inst Phys, CH-3012 Bern, Switzerland..
    Gombosi, T. I.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA..
    Gune, H.
    Belgian Inst Space Aeron BIRA IASB, B-1180 Brussels, Belgium..
    Hansen, K. C.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA..
    Haessig, M.
    SW Res Inst, Div Space Sci, San Antonio, TX 78228 USA..
    Jaeckel, A.
    Univ Bern, Inst Phys, CH-3012 Bern, Switzerland..
    Korth, A.
    Max Planck Inst Sonnensyst Forsch, D-37077 Gottingen, Germany..
    Le Roy, L.
    Univ Bern, Inst Phys, CH-3012 Bern, Switzerland..
    Mall, U.
    Max Planck Inst Sonnensyst Forsch, D-37077 Gottingen, Germany..
    Mandt, K. E.
    SW Res Inst, Div Space Sci, San Antonio, TX 78228 USA..
    Petrinec, S. M.
    Lockheed Martin Adv Technol Ctr, Palo Alto, CA 94304 USA..
    Raghuram, S.
    Univ London Imperial Coll Sci Technol & Med, Dept Phys, Space & Atmospher Phys Grp, London SW7 2AZ, England..
    Reme, H.
    Univ Toulouse, UPS OMP, IRAP, F-31028 Toulouse, France.;CNRS, IRAP, F-31028 Toulouse 4, France..
    Rinaldi, M.
    SW Res Inst, Div Space Sci, San Antonio, TX 78228 USA..
    Rubin, M.
    Univ Bern, Inst Phys, CH-3012 Bern, Switzerland..
    Semon, T.
    Univ Bern, Inst Phys, CH-3012 Bern, Switzerland..
    Trattner, K. J.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA..
    Tzou, C. -Y
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Waite, J. H.
    SW Res Inst, Div Space Sci, San Antonio, TX 78228 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Wurz, P.
    Univ Bern, Inst Phys, CH-3012 Bern, Switzerland..
    ROSINA/DFMS and IES observations of 67P: Ion-neutral chemistry in the coma of a weakly outgassing comet2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 583, article id A2Article in journal (Refereed)
    Abstract [en]

    Context. The Rosetta encounter with comet 67P/Churyumov-Gerasimenko provides a unique opportunity for an in situ, up-close investigation of ion-neutral chemistry in the coma of a weakly outgassing comet far from the Sun. Aims. Observations of primary and secondary ions and modeling are used to investigate the role of ion-neutral chemistry within the thin coma. Methods. Observations from late October through mid-December 2014 show the continuous presence of the solar wind 30 km from the comet nucleus. These and other observations indicate that there is no contact surface and the solar wind has direct access to the nucleus. On several occasions during this time period, the Rosetta/ROSINA/Double Focusing Mass Spectrometer measured the low-energy ion composition in the coma. Organic volatiles and water group ions and their breakup products (masses 14 through 19), COP, and CO, (masses 28 and 44) and other mass peaks (at masses 26, 27, and possibly 30) were observed. Secondary ions include H3O+ and HCO+ (masses 19 and 29). These secondary ions indicate ion-neutral chemistry in the thin coma of the comet. A relatively simple model is constructed to account for the low H3O /H2O+ and HCO /CO+ ratios observed in a water dominated coma. Results from this simple model are compared with results from models that include a more detailed chemical reaction network. Results. At low outgassing rates, predictions from the simple model agree with observations and with results from more complex models that include much more chemistry. At higher outgassing rates, the ion-neutral chemistry is still limited and high HCO /CO+ ratios are predicted and observed. However, at higher outgassing rates, the model predicts high H3O /H2O+ ratios and the observed ratios are often low. These low ratios may be the result of the highly heterogeneous nature of the coma, where CO and CO2 number densities can exceed that of water.

  • 327.
    Fuselier, S. A.
    et al.
    Southwest Res Inst, San Antonio, TX 78238 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Mukherjee, J.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    Denton, M. H.
    New Mexico Consortium, Los Alamos, NM USA..
    Petrinec, S. M.
    Lockheed Martin Adv Technol Ctr, Palo Alto, CA USA..
    Trattner, K. J.
    Univ Colorado, Atmospher & Space Phys Lab, Campus Box 392, Boulder, CO 80309 USA..
    Toledo-Redondo, S.
    Univ Toulouse, Inst Rech Astrophys & Planetol, CNRS, UPS,CNES, Toulouse, France..
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Aunai, N.
    Lab Phys Plasmas, Palaiseau, France..
    Chappell, C. R.
    Vanderbilt Univ, 221 Kirkland Hall, Nashville, TN 37235 USA..
    Glocer, A.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Haaland, S.
    Max Planck Inst, Katlenburg Lindau, Germany..
    Hesse, M.
    Univ Bergen, Bergen, Norway..
    Kistler, L. M.
    Univ New Hampshire, Durham, NH 03824 USA..
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, CNRS, UPS,CNES, Toulouse, France..
    Li, W. Y.
    Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Moore, T. E.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Graham, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Tenfjord, P.
    Univ Bergen, Bergen, Norway..
    Dargent, J.
    Univ Pisa, Phys Dept E Fermi, Pisa, Italy..
    Vines, S. K.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, Earth & Space Sci, Los Angeles, CA USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    High-density O+ in Earth's outer magnetosphere and its effect on dayside magnetopause magnetic reconnection2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 12, p. 10257-10269Article in journal (Refereed)
    Abstract [en]

    The warm plasma cloak is a source of magnetospheric plasma that contain significant O+. When the O+ density in the magnetosphere near the magnetopause is >0.2 cm(-3) and the H+ density is <1.5 cm(-3), then O+ dominates the magnetospheric ion mass density by more than a factor of 2. A survey is conducted of such O+-rich warm plasma cloak intervals and their effect on reconnection at the Earth's magnetopause. The survey uses data from the Magnetospheric Multiscale mission (MMS) and the results are compared and combined with a previous survey of the warm plasma cloak. Overall, the warm plasma cloak and the O+-rich warm plasma cloak reduce the magnetopause reconnection rate by >20% due to mass-loading only about 2% to 4% of the time. However, during geomagnetic storms, O+ dominates the mass density of the warm plasma cloak and these mass densities are very high. Therefore, a separate study is conducted to determine the effect of the warm plasma cloak on magnetopause reconnection during geomagnetically disturbed times. This study shows that the warm plasma cloak reduces the reconnection rate significantly about 25% of the time during disturbed conditions.

  • 328.
    Fuselier, S. A.
    et al.
    Southwest Res Inst, San Antonio, TX 78238 USA;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA.
    Trattner, K. J.
    Univ Colorado, Atmospher & Space Phys Lab, Campus Box 392, Boulder, CO 80309 USA.
    Petrinec, S. M.
    Lockheed Martin Adv Technol Ctr, Palo Alto, CA USA.
    Denton, M. H.
    New Mexico Consortium, Los Alamos, NM USA.
    Toledo-Redondo, S.
    Univ Toulouse, Inst Rech Astrophys & Planetol, CNRS, UPS,CNES, Toulouse, France.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Aunai, N.
    Lab Phys Plasmas, Paris, France.
    Chappell, C. R.
    Vanderbilt Univ, Dept Phys & Astron, Nashville, TN 37235 USA.
    Glocer, A.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Haaland, S. E.
    Max Planck Inst Solar Syst Res, Gottingen, Germany;Univ Bergen, Birkeland Ctr Space Sci, Bergen, Norway.
    Hesse, M.
    Univ Bergen, Birkeland Ctr Space Sci, Bergen, Norway.
    Kistler, L. M.
    Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA.
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, CNRS, UPS,CNES, Toulouse, France.
    Li, W.
    Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China.
    Moore, T. E.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Alm, Love
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Tenfjord, P.
    Univ Bergen, Birkeland Ctr Space Sci, Bergen, Norway.
    Dargent, J.
    Univ Pisa, Phys Dept E Fermi, Pisa, Italy.
    Vines, S. K.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA.
    Nykyri, K.
    Embry Riddle Aeronaut Univ, Ctr Space & Atmospher Res, Daytona Beach, FL USA.
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78238 USA.
    Strangeway, R. J.
    Univ Calif Los Angeles, Earth & Space Sci, Los Angeles, CA USA.
    Mass Loading the Earth's Dayside Magnetopause Boundary Layer and Its Effect on Magnetic Reconnection2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 12, p. 6204-6213Article in journal (Refereed)
    Abstract [en]

    When the interplanetary magnetic field is northward for a period of time, O+ from the high-latitude ionosphere escapes along reconnected magnetic field lines into the dayside magnetopause boundary layer. Dual-lobe reconnection closes these field lines, which traps O+ and mass loads the boundary layer. This O+ is an additional source of magnetospheric plasma that interacts with magnetosheath plasma through magnetic reconnection. This mass loading and interaction is illustrated through analysis of a magnetopause crossing by the Magnetospheric Multiscale spacecraft. While in the O+-rich boundary layer, the interplanetary magnetic field turns southward. As the Magnetospheric Multiscale spacecraft cross the high-shear magnetopause, reconnection signatures are observed. While the reconnection rate is likely reduced by the mass loading, reconnection is not suppressed at the magnetopause. The high-latitude dayside ionosphere is therefore a source of magnetospheric ions that contributes often to transient reduction in the reconnection rate at the dayside magnetopause.

  • 329.
    Fuselier, S. A.
    et al.
    Southwest Res Inst, San Antonio, TX 78238 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Vines, S. K.
    Southwest Res Inst, San Antonio, TX 78238 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA.;Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    Petrinec, S. M.
    Lockheed Martin Adv Technol Ctr, Palo Alto, CA USA..
    Trattner, K. J.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Cassak, P. A.
    West Virginia Univ, Dept Phys & Astron, Morgantown, WV 26506 USA..
    Chen, L. -J
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Eriksson, S.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Giles, B. L.
    Goddard Space Flight Ctr, Greenbelt, MD USA..
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Plantol, Toulouse, France.;CNRS, Toulouse, France..
    Lewis, W. S.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    Mukherjee, J.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    Norgren, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Phan, T. -D
    Russell, C. T.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA..
    Torbert, R. B.
    Southwest Res Inst, San Antonio, TX 78238 USA.;Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Webster, J. M.
    Rice Univ, Phys & Astron, Houston, TX USA..
    Large-scale characteristics of reconnection diffusion regions and associated magnetopause crossings observed by MMS2017In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 5, p. 5466-5486Article in journal (Refereed)
    Abstract [en]

    The Magnetospheric Multiscale (MMS) mission was designed to make observations in the very small electron diffusion region (EDR), where magnetic reconnection takes place. From a data set of over 4500 magnetopause crossings obtained in the first phase of the mission, MMS had encounters near or within 12 EDRs. These 12 events and associated magnetopause crossings are considered as a group to determine if they span the widest possible range of external and internal conditions (i.e., in the solar wind and magnetosphere). In addition, observations from MMS are used to determine if there are multiple X-lines present and also to provide information on X-line location relative to the spacecraft. These 12 events represent nearly the widest possible range of conditions at the dayside magnetopause. They occur over a wide range of local times and magnetic shear angles between the magnetosheath and magnetospheric magnetic fields. Most show evidence for multiple reconnection sites.

  • 330.
    Futaana, Yoshifumi
    et al.
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden.
    Barabash, Stas
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden.
    Wieser, Martin
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden.
    Wurz, Peter
    Univ Bern, Bern, Switzerland.
    Hurley, Dana
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA.
    Horanyi, Mihaly
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.
    Mall, Urs
    Max Planck Inst Solar Syst Res, Gottingen, Germany.
    Andre, Nicolas
    Univ Toulouse, CNRS, IRAP, Toulouse, France.
    Ivchenko, Nickolay
    KTH Royal Inst Technol, Stockholm, Sweden.
    Oberst, Juergen
    German Aerosp Ctr, Berlin, Germany.
    Retherford, Kurt
    Southwest Res Inst, San Antonio, TX USA.
    Coates, Andrew
    UCL, Mullard Space Sci Lab, London, England.
    Masters, Adam
    Imperial Coll London, London, England.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Kallio, Esa
    Aalto Univ, Helsinki, Finland.
    SELMA mission: How do airless bodies interact with space environment? The Moon as an accessible laboratory2018In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 156, p. 23-40Article in journal (Refereed)
    Abstract [en]

    The Moon is an archetypal atmosphere-less celestial body in the Solar System. For such bodies, the environments are characterized by complex interaction among the space plasma, tenuous neutral gas, dust and the outermost layer of the surface. Here we propose the SELMA mission (Surface, Environment, and Lunar Magnetic Anomalies) to study how airless bodies interact with space environment. SELMA uses a unique combination of remote sensing via ultraviolet and infrared wavelengths, and energetic neutral atom imaging, as well as in situ measurements of exospheric gas, plasma, and dust at the Moon. After observations in a lunar orbit for one year, SELMA will conduct an impact experiment to investigate volatile content in the soil of the permanently shadowed area of the Shackleton crater. SELMA also carries an impact probe to sound the Reiner-Gamma mini-magnetosphere and its interaction with the lunar regolith from the SELMA orbit down to the surface. SELMA was proposed to the European Space Agency as a medium-class mission (M5) in October 2016. Research on the SELMA scientific themes is of importance for fundamental planetary sciences and for our general understanding of how the Solar System works. In addition, SELMA outcomes will contribute to future lunar explorations through qualitative characterization of the lunar environment and, in particular, investigation of the presence of water in the lunar soil, as a valuable resource to harvest from the lunar regolith.

  • 331.
    Futaana, Yoshifumi
    et al.
    Swedish Inst Space Phys, SE-98128 Kiruna, Sweden.
    Wang, Xiao-Dong
    Swedish Inst Space Phys, Solar Syst Phys & Space Technol Grp, SE-98128 Kiruna, Sweden.
    Roussos, Elias
    Max Planck Inst Solar Syst Res, D-37077 Gottingen, Germany.
    Krupp, Norbert
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ågren, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Fränz, Markus
    Barabash, Stas
    Swedish Inst Space Phys, SE-98128 Kiruna, Sweden.
    Lei, Fan
    RadMod Res Ltd, Camberley GU15 2PD, England.
    Heynderickx, Daniel
    DH Consultancy BVBA, B-3000 Leuven, Belgium.
    Truscott, Pete
    Kallisto Consultancy Ltd, Farnborough GU14 9AJ, Hants, England.
    Cipriani, Fabrice
    European Space Agcy, European Space Res & Technol Ctr, NL-2200 AG Noordwijk, Netherlands.
    Rodgers, David
    European Space Agcy, European Space Res & Technol Ctr, NL-2200 AG Noordwijk, Netherlands.
    Corotation Plasma Environment Model: An Empirical Probability Model of the Jovian Magnetosphere2018In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 46, no 6, p. 2126-2145Article in journal (Refereed)
    Abstract [en]

    We developed a new empirical model for corotating plasma in the Jovian magnetosphere. The model, named the corotation plasma environment model version 2 (CPEMv2), considers the charge density, velocity vector, and ion temperature based on Galileo/plasma system (PLS) ion data. In addition, we develop hot electron temperature and density models based on Galileo/PLS electron data. All of the models provide respective quantities in the magnetic equator plane of 9-30RJ, while the charge density model can be extended to 3-D space. A characteristic feature of the CPEM is its support of the percentile as a user input. This feature enables us to model extreme conditions in addition to normal states. In this paper, we review the foundations of the new empirical model, present a general derivation algorithm, and offer a detailed formulation of each parameter of the CPEMv2. As all CPEM parameters are of the analytical form, their implementation is straightforward, and execution involves the use of a small number of computational resources. The CPEM is flexible; for example, it can be extended, as new data (from observations or simulation results) become available. The CPEM can be used for the mission operation of the European Space Agency's mission to Jupiter, JUpiter ICy moons Explorer (JUICE), and for future data analyses.

  • 332.
    Galand, M.
    et al.
    Imperial Coll London, Dept Phys, London, England..
    Feldman, P. D.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA..
    Bockelee-Morvan, D.
    Univ Paris, Sorbonne Univ, Univ PSL, CNRS,Observ Paris,LESIA, Meudon, France..
    Biver, N.
    Univ Paris, Sorbonne Univ, Univ PSL, CNRS,Observ Paris,LESIA, Meudon, France..
    Cheng, Y. -C
    Rinaldi, G.
    INAF, IAPS, Rome, Italy..
    Rubin, M.
    Univ Bern, Phys Inst, Bern, Switzerland..
    Altwegg, K.
    Univ Bern, Phys Inst, Bern, Switzerland..
    Deca, J.
    Univ Colorado, Lab Atmospher & Space Phys LASP, Boulder, CO 80309 USA.;NASA, Inst Modeling Plasma Atmospheres & Cosm Dust, SSERVI, Moffett Field, CA USA..
    Beth, A.
    Imperial Coll London, Dept Phys, London, England..
    Stephenson, P.
    Imperial Coll London, Dept Phys, London, England..
    Heritier, K. L.
    Imperial Coll London, Dept Phys, London, England..
    Henri, P.
    Univ Orleans, CNRS, LPC2E, Orleans, France..
    Parker, J. Wm.
    Southwest Res Inst, Dept Space Studies, Boulder, CO USA..
    Carr, C.
    Imperial Coll London, Dept Phys, London, England..
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Burch, J.
    Southwest Res Inst, San Antonio, TX USA..
    Far-ultraviolet aurora identified at comet 67P/Churyumov-Gerasimenko2020In: Nature Astronomy, E-ISSN 2397-3366, Vol. 4, no 11, p. 1084-1091Article in journal (Refereed)
    Abstract [en]

    In situ measurements from the Rosetta spacecraft reveal the presence of atomic emissions close to comet 67P's nucleus. Such emissions are due to dissociative excitation of molecules by the interaction with the solar wind, identifying them as a form of aurora. Having a nucleus darker than charcoal, comets are usually detected from Earth through the emissions from their coma. The coma is an envelope of gas that forms through the sublimation of ices from the nucleus as the comet gets closer to the Sun. In the far-ultraviolet portion of the spectrum, observations of comae have revealed the presence of atomic hydrogen and oxygen emissions. When observed over large spatial scales as seen from Earth, such emissions are dominated by resonance fluorescence pumped by solar radiation. Here, we analyse atomic emissions acquired close to the cometary nucleus by the Rosetta spacecraft and reveal their auroral nature. To identify their origin, we undertake a quantitative multi-instrument analysis of these emissions by combining coincident neutral gas, electron and far-ultraviolet observations. We establish that the atomic emissions detected from Rosetta around comet 67P/Churyumov-Gerasimenko at large heliocentric distances result from the dissociative excitation of cometary molecules by accelerated solar-wind electrons (and not by electrons produced from photo-ionization of cometary molecules). Like the discrete aurorae at Earth and Mars, this cometary aurora is driven by the interaction of the solar wind with the local environment. We also highlight how the oxygen line Oiat wavelength 1,356 A could be used as a tracer of solar-wind electron variability.

  • 333.
    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 University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    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 University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Glassmeier, K. -H
    Johansson, Fredrik L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    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 University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    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 Sun2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, p. S331-S351Article in journal (Refereed)
    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.

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  • 334. Galand, M.
    et al.
    Yelle, R. V.
    Coates, A. J.
    Backes, H.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Electron temperature of Titan's sunlit ionosphere2006In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 33, no 21, p. L21101-Article in journal (Refereed)
    Abstract [en]

    Titan's upper atmosphere is ionized by solar radiation and particle bombardment from Saturn's magnetosphere. The induced ionosphere plays a key role in the coupling of Titan's atmosphere with the Kronian environment. It also provides unique signatures for identifying energy sources upon Titan's upper atmosphere. Here we focus on observations from the first, close flyby by the Cassini spacecraft and assess the ionization and electron heating sources in Titan's sunlit ionosphere. We compare CAPS electron spectra with spectra produced by an electron transport model based on the INMS neutral densities and a MHD interaction model. In addition, we compare RPWS electron temperature against the models. The important terms in the electron energy equation include loss through excitation of vibrational states of N-2 and CH4, Coulomb collisions with suprathermal electrons, and thermal conduction. Our analysis highlights the important role of the magnetic field line configuration for aeronomic studies at Titan.

  • 335. Galand, Marina
    et al.
    Yelle, Roger
    Cui, Jun
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vuitton, Veronique
    Wellbrock, Anne
    Coates, Andrew
    Ionization sources in Titan's deep ionosphere2010In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 115, p. A07312-Article in journal (Refereed)
    Abstract [en]

    We analyze a multi-instrumental data set from four Titan encounters by the Cassini spacecraft to investigate in detail the formation of the ionosphere. The data set includes observations of thermospheric and ionospheric species and suprathermal electrons. A model describing the solar and electron energy deposition is used as an organizing element of the Cassini data set. We first compare the calculated secondary electron production rates with the rates inferred from suprathermal electron intensity measurements. We then calculate an effective electron dissociative recombination coefficient, applying three different approaches to the Cassini data set. Our findings are threefold: (1) The effective recombination coefficient derived under sunlit conditions in the deep ionosphere (< 1200 km) is found to be independent of solar zenith angle and flyby. Its value ranges from 6.9 x 10(-7) cm(3) s(-1) at 1200 km to 5.9 x 10(-6) cm(3) s(-1) at 970 km at 500 K. (2) The presence of an additional, minor source of ionization is revealed when the solar contribution is weak enough. The contribution by this non-solar source-energetic electrons most probably of magnetospheric origin-becomes apparent for secondary electron production rates, due to solar illumination alone, close to or smaller than about 3 x 10(-1) cm(-3) s(-1). Such a threshold is reached near the solar terminator below the main solar-driven electron production peak (< 1050 km). (3) Our ability to model the electron density in the deep ionosphere is very limited. Our findings highlight the need for more laboratory measurements of electron dissociative recombination coefficients for heavy ion species at high electron temperatures (especially near 500 K).

  • 336. Gamier, P.
    et al.
    Holmberg, Mika K. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, J. -E
    Lewis, G. R.
    Schippers, P.
    Coates, A.
    Gurnett, D. A.
    Waite, J. H.
    Dandouras, I.
    Deriving the characteristics of warm electrons (100-500 eV) in the magnetosphere of Saturn with the Cassini Langmuir probe2014In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 104, p. 173-184Article in journal (Refereed)
    Abstract [en]

    Though Langmuir probes (LP) are designed to investigate cold plasma regions (e.g. ionospheres), a recent analysis revealed a strong sensitivity of the Cassini LP measurements to hundreds of eV electrons. These warm electrons impact the surface of the probe and generate a significant current of secondary electrons, that impacts both the DC level and the slope of the current-voltage curve of the LP (for negative potentials) through energetic contributions that may be modeled with a reasonable precision. We show here how to derive information about the incident warm electrons from the analysis of these energetic contributions, in the regions where the cold plasma component is small with an average temperature in the range similar to [100-500] eV. First, modeling the energetic contributions (based on the incident electron flux given by a single anode of the CAPS spectrometer) allows us to provide information about the pitch angle anisotropies of the incident hundreds of eV electrons. The modeling reveals indeed sometimes a large variability of the estimated maximum secondary electron yield (which is a constant for a surface material) needed to reproduce the observations. Such dispersions give evidence for strong pitch angle anisotropies of the incident electrons, and using a functional form of the pitch angle distribution even allows us to derive the real peak angle of the distribution. Second, rough estimates of the total electron temperature may be derived in the regions where the warm electrons are dominant and thus strongly influence the LP observations, i.e. when the average electron temperature is in the range similar to [100-500] eV. These regions may be identified from the LP observations through large positive values of the current-voltage slope at negative potentials. The estimated temperature may then be used to derive the electron density in the same region, with estimated densities between similar to 0.1 and a few particles/cm(3) (cc). The derived densities are in better agreement with the CAPS measurements than the values derived from the proxy technique (Morooka et al., 2009) based on the floating potential of the LP. Both the electron temperature and the density estimates lie outside the classical capabilities of the LP, which are essentially n(e) > 5 cc and T-e <5 eV at Saturn. This approximate derivation technique may be used in the regions where the cold plasma component is small with an average temperature in the range similar to [100-500] eV, which occurs often in the L range 6.4-9.4 R-S when Cassini is off the equator, but may occur anywhere in the magnetosphere. This technique may be all the more interesting since the CAPS instrument was shut down, and, though it cannot replace the CAPS instrument, the technique can provide useful information about the electron moments, with probably even better estimates than CAPS in some cases (when the plasma is strongly anisotropic). Finally, a simple modeling approach allows us to predict the impact of the energetic contributions on LP measurements in any plasma environment whose characteristics (density, temperature, etc.) are known. LP observations may thus be influenced by warm electrons in several planetary plasma regions in the solar system, and ambient magnetospheric electron density and temperature could be estimated in some of them (e.g. around several galilean satellites) through the use of Langmuir probes.

  • 337.
    Gao, C. -H
    et al.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China.;Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing, Peoples R China..
    Tang, B. -B
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Li, W. Y.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Wang, C.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China.;Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing, Peoples R China..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Gershman, D. J.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Rager, A. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.;Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Lindqvist, P. -A
    KTH Royal Inst Technol, Sch Elect Engn, Space & Plasma Phys, Stockholm, Sweden..
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Effect of the Electric Field on the Agyrotropic Electron Distributions2021In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 48, no 5, article id e2020GL091437Article in journal (Refereed)
    Abstract [en]

    We investigate agyrotropic electron distributions from two magnetopause events observed by magnetospheric multiscale (MMS) spacecraft. Agyrotropic electron distributions can be generated by the finite electron gyration at an electron-scale boundary, and the electric field normal to this boundary usually contributes to the electron acceleration to make the agyrotropic distributions more apparent. The effect of the electric field becomes important only when it is sufficiently strong and local, meaning its electrostatic potential is comparable to or larger than the electron temperature, and its width is smaller than the electron thermal gyroradius, so that this electric field can directly accelerate part of the electrons out of the original core to form agyrotropic electron distributions. Also, we reproduce the measured electron "finger" structures from test particle simulations, which can be effectively suppressed by increasing the sampling rate of the electron measurement. Plain Language Summary Agyrotropic electron distributions reveal valuable information of electron dynamics at electron scales, and the generation of these distributions have been extensively studied. In this study, we provide a new possibility to generate agyrotropic electron distributions with a strong localized electric field, which can accelerate part of electrons out of the original electron core to form agyrotropic distributions. As such large-amplitude small-scale electric field fluctuations are frequently observed in turbulent plasma environments, we suggest that more agyrotropic electron distributions can be observed with high temporal resolution measurements.

  • 338.
    Gao, C.-H.
    et al.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China.;Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing, Peoples R China..
    Tang, B.-B.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Guo, X.-C.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Li, W. Y.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Turner, D. L.
    Aerosp Corp, Space Sci Dept, El Segundo, CA USA..
    Yang, Z. W.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Wang, C.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China.;Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing, Peoples R China..
    Agyrotropic Electron Distributions in the Terrestrial Foreshock Transients2023In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 50, no 4, article id e2022GL102235Article in journal (Refereed)
    Abstract [en]

    Agyrotropic electron distributions are frequently taken as an indicator of electron diffusion regions of magnetic reconnection. However, they have also been found at electron-scale boundaries of the non-reconnecting magnetopause and are generated by the electron finite gyroradius effect. Here, we present magnetospheric multiscale observations of agyrotropic electron distributions in the foreshock region. These distributions are generated by the electron finite gyroradius effect after magnetic curvature scattering at a thin electron-scale boundary. Meanwhile, the signatures of magnetic reconnection are absent at this boundary. The test-particle simulation is adopted to verify the generation of the agyrotropic electron distributions by assuming one-dimensional magnetic geometry. These observations suggest that agyrotropic electron distributions can be more widely formed at electron-scale boundaries in space plasma environment.

    Plain Language Summary

    The agyrotropic electron distributions, which could be unstable to generate high frequency electrostatic waves, reveal valuable information of electron dynamics at electron scales. However, due to electron's small mass, the related observational study becomes only possible with the high-resolution magnetospheric multiscale data. In this study, we show that the agyrotropic electron distributions can be also formed in the foreshock transients such as inside an hot flow anomaly, suggesting that agyrotropic electron distributions are ubiquitous in space plasma.

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  • 339.
    García Ribas, Alberto
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    WSA-ENLIL + Cone ensemble modeling of an Earth-directed ICME: Comparison with in-situ observations by Solar Orbiter and WIND at L12023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Coronal mass ejections (CMEs) are considered the most energetic phenomenon in the heliosphere. Originated in the solar corona, they are formed by ejected plasma driven by strong magnetic fields. Studying the effects of CMEs on Earth and the interplanetary medium has become priority, since ground- and space-based technology can be affected by strong CMEs. Modeling of CMEs can provide an estimation of the arrival time, and WSA-ENLIL + Cone model is one of the most used models in space weather forecasting around the world. The WSA-ENLIL + Cone model is based on the characterization of the observed coronagraph image of a CME as a projected cone in the plane-of-sky (POS), the use of a synoptic magnetogram and the magnetohydrodynamical approximation to model CME events. In this project, we will study a particular event occurred on the 2021-11-03 and compare it with simulated data using the WSA-ENLIL + Cone model. The main objective is to study the input parameters of the model and assess the forecasting ability of the simulations. To do so, we have used in-situ data obtained from the Solar Orbiter spacecraft (SolO) and WIND spacecraft, that at the time of the event were located over the same line-of-sight, being located at 0.8 AU and the L1 Lagrange point, respectively. A total of 144 runs (divided in 6 ensembles of 24 simulated runs) were provided by the Met Office (UK) for each spacecraft location. Each simulation run has been generated using preset input parameters with small random variations and a different background synoptic magnetogram. Statistical analysis has been carried out, showing a linear relationship between the half-width and the arrival velocity of the CME. No particular relationship has been found between the input parameters and the time of arrival (ToA) of simulated runs, probably due to the small range of variation. Late initialized synoptic maps seems to produce better ToA prediction.

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  • 340.
    Garnier, P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dandouras, I.
    Toublanc, D.
    Roelof, E. C.
    Brandt, P. C.
    Mitchell, D. G.
    Krimigis, S. M.
    Krupp, N.
    Hamilton, D. C.
    Dutuit, O.
    Wahlund, Jan Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    The lower exosphere of Titan: Energetic neutral atoms absorption and imaging2008In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 113, no A10, p. A10216-Article in journal (Refereed)
    Abstract [en]

    The Saturn magnetosphere interacts with the Titan atmosphere through various mechanisms. One of them leads, by charge exchange reactions between the energetic Saturnian ions and the exospheric neutrals of Titan, to the production of energetic neutral atoms (ENAs). The Ion and Neutral Camera (INCA), one of the three sensors that comprise the Magnetosphere Imaging Instrument (MIMI) on the Cassini/Huygens mission to Saturn and Titan, images the ENA emissions in the Saturnian magnetosphere. This study focuses on the ENA imaging of Titan (for 20-50 keV H ENAs), with the example of the Ta Titan flyby (26 October 2004): our objective is to understand the positioning of the ENA halo observed around Titan. Thus we investigate the main ENA loss mechanisms, such as the finite gyroradii effects for the parent ions, or the charge stripping with exospheric neutrals. We show that multiple stripping and charge exchange reactions have to be taken into account to understand the ENA dynamics. The use of an analytical approach, taking into account these reactions, combined with a reprocessing of the INCA data, allows us to reproduce the ENA images of the Ta flyby and indicates a lower limit for ENA emission around the exobase. However, the dynamics of energetic particle through the Titan atmosphere remains complex, with an inconsistency between the ENA imaging at low and high altitudes.

  • 341. Garnier, P.
    et al.
    Dandouras, I.
    Toublanc, D.
    Roelof, E. C.
    Brandt, P. C.
    Mitchell, D. G.
    Krimigis, S. M.
    Krupp, N.
    Hamilton, D. C.
    Wahlund, Jan Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Statistical analysis of the energetic ion and ENA data for the Titan environment2010In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 58, no 14-15, p. 1811-1822Article in journal (Refereed)
    Abstract [en]

    The MIMI experiment (Magnetosphere Imaging Instrument) onboard Cassini is dedicated to the study of energetic particles, with in particular LEMMS analyzing charged particles, or the INCA detector which can image the Energetic Neutral Atoms produced by charge exchange collisions between cold neutrals and energetic ions. The MIMI experiment is thus well adapted to the study of the interaction between the Titan nitrogen rich atmosphere and the energetic Saturnian magnetospheric plasma. We analyze here the energetic protons at the Titan orbit crossings before January 2008 (MIMI-LEMMS data; 27-255 key), which are very dynamic, with tri-modal flux spectra and probably quasi-isotropic pitch angle distributions. We provide statistical parameters for the proton fluxes, leading to estimates of the average energy deposition into Titan's atmosphere, before we discuss the possible influence of Titan on the magnetopause. We then analyze the H ENA images (24-55 key) during the Titan flybys before June 2006 to obtain a better diagnostic of the Titan interaction: the ENAs variability is mostly related to the magnetospheric variability (the exosphere being roughly stable) or the distance from the moon, the ENAs halo around Titan is very stable (corresponding to a lower limit for ENAs emission at the exobase), and strong asymmetries are observed, due to finite gyroradii effects for the parent ions.

  • 342.
    Garnier, P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Rosenqvist, Lisa
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Modolo, Ronan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ågren, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Sergis, N.
    Canu, P.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Gurnett, D. A.
    Kurth, W. S.
    Krimigis, S. M.
    Coates, A.
    Dougherty, M.
    Waite, J. H.
    Titan's ionosphere in the magnetosheath: Cassini RPWS results during the T32 flyby2009In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 27, no 11, p. 4257-4272Article in journal (Refereed)
    Abstract [en]

    The Cassini mission has provided much information about the Titan environment, with numerous low altitude encounters with the moon being always inside the magnetosphere. The only encounter taking place outside the magnetopause, in the magnetosheath, occurred the 13 June 2007 (T32 flyby). This paper is dedicated to the analysis of the Radio and Plasma Wave investigation data during this specific encounter, in particular with the Langmuir probe, providing a detailed picture of the cold plasma environment and of Titan's ionosphere with these unique plasma conditions. The various pressure terms were also calculated during the flyby. The comparison with the T30 flyby, whose geometry was very similar to the T32 encounter but where Titan was immersed in the kronian magnetosphere, reveals that the evolution of the incident plasma has a significant influence on the structure of the ionosphere, with in particular a change of the exo-ionospheric shape. The electrical conductivities are given along the trajectory of the spacecraft and the discovery of a polar plasma cavity is reported.

  • 343. Garnier, P.
    et al.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Holmberg, Madeleine
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Grimald, S.
    Morooka, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Gurnett, D. A.
    Kurth, W. S.
    Mapping 300 eV electrons at Saturn with the Cassini RPWS Langmuir probe2011In: EPSC-DPS Joint Meeting 2011, 2011Conference paper (Refereed)
    Abstract [en]

    The Cassini Langmuir probe (onboard RPWS experiment) has provided wealth of information about the kronian cold plasma environment since the Saturn Orbit Insertion in 2004. The usage of the Langmuir probe is based on the fitting of the currentvoltage curve which brings information on several plasma parameters in cold and dense plasma regions. The ion part of the I-V curve may however be influenced by energetic particles hitting the probe, leading to an enhanced ion current measured. We report here the influence of 300 eV electrons on the probe current, with a current belt observed between Dione and Rhea.

  • 344. Garnier, P.
    et al.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Holmberg, Madeleine K. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Morooka, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Grimald, S.
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Schippers, P.
    Gurnett, D. A.
    Krimigis, S. M.
    Krupp, N.
    Coates, A.
    Crary, F.
    Gustafsson, Georg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    The detection of energetic electrons with the Cassini Langmuir probe at Saturn2012In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, p. A10202-Article in journal (Refereed)
    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.

  • 345.
    Garnier, Philippe
    et al.
    Institut de Recherche en Astrophysique et Planétologie (IRAP).
    Holmberg, Mika
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Lewis, G R
    Grimald, S Rochel
    Thomsen, M F
    Gurnetti, D A
    Coates, A J
    Crary, F J
    Dandouras, I
    The influence of the secondary electrons induced by energetic electrons impacting the Cassini Langmuir probe at Saturn2013In: Journal of geophysical research Space Physics, ISSN 2169-9402, Vol. 118, no 11, p. 7054-7073Article in journal (Refereed)
    Abstract [en]

    The Cassini Langmuir Probe (LP) onboard the Radio and Plasma Wave Science experiment has provided much information about the Saturnian cold plasma environment since the Saturn Orbit Insertion in 2004. A recent analysis revealed that the LP is also sensitive to the energetic electrons (250–450 eV) for negative potentials. These electrons impact the surface of the probe and generate a current of secondary electrons, inducing an energetic contribution to the DC level of the current-voltage (I-V) curve measured by the LP. In this paper, we further investigated this influence of the energetic electrons and (1) showed how the secondary electrons impact not only the DC level but also the slope of the (I-V) curve with unexpected positive values of the slope, (2) explained how the slope of the (I-V) curve can be used to identify where the influence of the energetic electrons is strong, (3) showed that this influence may be interpreted in terms of the critical and anticritical temperatures concept detailed by Lai and Tautz (2008), thus providing the first observational evidence for the existence of the anticritical temperature, (4) derived estimations of the maximum secondary yield value for the LP surface without using laboratory measurements, and (5) showed how to model the energetic contributions to the DC level and slope of the (I-V) curve via several methods (empirically and theoretically). This work will allow, for the whole Cassini mission, to clean the measurements influenced by such electrons. Furthermore, the understanding of this influence may be used for other missions using Langmuir probes, such as the future missions Jupiter Icy Moons Explorer at Jupiter, BepiColombo at Mercury, Rosetta at the comet Churyumov-Gerasimenko, and even the probes onboard spacecrafts in the Earth magnetosphere.

  • 346. Gedalin, M.
    et al.
    Medvedev, M.
    Spitkovsky, A.
    Krasnoselskikh, V.
    Balikhin, M.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Perri, S.
    Growth of filaments and saturation of the filamentation instability2010In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 17, no 3, p. 032108-Article in journal (Refereed)
    Abstract [en]

    The filamentation instability of counterstreaming beams is a nonresonant hydrodynamic-type instability whose growth rate is a smooth function of the wavelength (scale). As a result, perturbations with all unstable wavelengths develop, and the growth saturates due to the saturation of available current. For a given scale, the magnetic field at saturation is proportional to the scale. As a result, the instability develops in a nearly linear regime, where the unstable modes stop growing as soon as the saturation of the corresponding wavelength is reached. At each moment there exists a dominant scale of the magnetic field which is the scale that reached saturation at this particular time. The smaller scales do not disappear and can be easily distinguished in the current structure. The overall growth of the instability stops when the loss of the streaming ion energy because of deceleration is comparable to the initial ion energy.

  • 347. Gedalin, M.
    et al.
    Spitkovsky, A.
    Medvedev, M.
    Balikhin, M.
    Krasnoselskikh, V.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Perri, S.
    Relativistic filamentary equilibria2011In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 77, p. 193-205Article in journal (Refereed)
    Abstract [en]

    Plasma filamentation is often encountered in collisionless shocks and inertial confinement fusion. We develop a general analytical description of the two-dimensional relativistic filamentary equilibrium and derive the conditions for existence of potential-free equilibria. A pseudopotential equation for the vector-potential is constructed for cold and relativistic Maxwellian distributions. The role of counter-streaming is explained. We present single current sheet and periodic current sheet solutions, and analyze the equilibria with electric potential. These solutions can be used to study linear and nonlinear evolution of the relativistic filamentation instability.

  • 348.
    Gedalin, Michael
    et al.
    Bengur Univ Negev, Dept Phys, Beer Sheva, Israel..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Russell, Christopher T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Pogorelov, Nikolai V.
    Univ Alabama Huntsville, Ctr Space Plasma & Aeron Res, Huntsville, AL 35805 USA..
    Roytershteyn, Vadim
    Space Sci Inst, Boulder, CO 80301 USA..
    Role of the overshoot in the shock self-organization2023In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 89, no 2, article id 905890201Article in journal (Refereed)
    Abstract [en]

    A collisionless shock is a self-organized structure where fields and particle distributions are mutually adjusted to ensure a stable mass, momentum and energy transfer from the upstream to the downstream region. This adjustment may involve rippling, reformation or whatever else is needed to maintain the shock. The fields inside the shock front are produced due to the motion of charged particles, which is in turn governed by the fields. The overshoot arises due to the deceleration of the ion flow by the increasing magnetic field, so that the drop of the dynamic pressure should be compensated by the increase of the magnetic pressure. The role of the overshoot is to regulate ion reflection, thus properly adjusting the downstream ion temperature and kinetic pressure and also speeding up the collisionless relaxation and reducing the anisotropy of the eventually gyrotropized distributions.

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  • 349.
    Gedalin, Michael
    et al.
    Ben Gur Univ Negev, Dept Phys, Beer Sheva, Israel..
    Golbraikh, Ephim
    Ben Gur Univ Negev, Dept Phys, Beer Sheva, Israel..
    Russell, Christopher T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Theory Helps Observations: Determination of the Shock Mach Number and Scales From Magnetic Measurements2022In: Frontiers in Physics, E-ISSN 2296-424X, Vol. 10, article id 852720Article in journal (Refereed)
    Abstract [en]

    The Mach number is one of the key parameters of collisionless shocks. Understanding shock physics requires knowledge of the spatial scales in the shock transition layer. The standard methods of determining the Mach number and the spatial scales require simultaneous measurements of the magnetic field and the particle density, velocity, and temperature. While magnetic field measurements are usually of high quality and resolution, particle measurements are often either unavailable or not properly adjusted to the plasma conditions. We show that theoretical arguments can be used to overcome the limitations of observations and determine the Mach number and spatial scales of the low-Mach number shock when only magnetic field data are available.

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  • 350.
    Gedalin, Michael
    et al.
    Ben Gurion Univ Negev, Dept Phys, Beer Sheva, Israel..
    Russell, Christopher T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Dimmock, Andrew P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Shock Mach Number Estimates Using Incomplete Measurements2021In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 126, no 10, article id e2021JA029519Article in journal (Refereed)
    Abstract [en]

    The Mach number is one of the most important parameters of collisionless shocks. The accuracy of its observational determination is compromised by several complications. Incomplete measurements of plasma parameters significantly contribute to the uncertainty, along with the errors of the normal determination. A set of CLUSTER observed shocks is analyzed using several methods for finding the shock normal and to circumvent the shortcomings of the plasma data. A relation between the maximum magnetic compression and the Alfvenic Mach number is established. It is proposed as a proxy for the Mach number estimate when measurements are incomplete.

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    fulltext
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