Logo: to the web site of Uppsala University

uu.sePublications from Uppsala University
Change search
Link to record
Permanent link

Direct link
Alternative names
Publications (10 of 39) Show all publications
Xystouris, G., Arridge, C. S., Morooka, M. & Wahlund, J.-E. (2023). Estimating the optical depth of Saturn's main rings using the Cassini Langmuir Probe. Monthly notices of the Royal Astronomical Society, 526(4), 5839-5860
Open this publication in new window or tab >>Estimating the optical depth of Saturn's main rings using the Cassini Langmuir Probe
2023 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 526, no 4, p. 5839-5860Article in journal (Refereed) Published
Abstract [en]

A Langmuir Probe (LP) measures currents from incident charged particles as a function of the applied bias voltage. While onboard a spacecraft the particles are either originated from the surrounding plasma, or emitted (e.g. through photoemission) from the spacecraft itself. The obtained current-voltage curve reflects the properties of the plasma in which the probe is immersed into, but also any photoemission due to illumination of the probe surface: As photoemission releases photoelectrons into space surrounding the probe, these can be recollected and measured as an additional plasma population. This complicates the estimation of the properties of the ambient plasma around the spacecraft. The photoemission current is sensitive to the extreme ultraviolet (UV) part of the spectrum, and it varies with the illumination from the Sun and the properties of the LP surface material, and any variation in the photoelectrons irradiance can be measured as a change in the current voltage curve. Cassini was eclipsed multiple times by Saturn and the main rings over its 14 yr mission. During each eclipse the LP recorded dramatic changes in the current-voltage curve, which were especially variable when Cassini was in shadow behind the main rings. We interpret these variations as the effect of spatial variations in the optical depth of the rings and hence use the observations to estimate the optical depth of Saturn's main rings. Our estimates are comparable with UV optical depth measurements from Cassini's remote sensing instruments.

Place, publisher, year, edition, pages
Oxford University Press, 2023
Keywords
opacity, plasmas, instrumentation: miscellaneous, eclipses, planets and satellites: rings
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-517521 (URN)10.1093/mnras/stad2793 (DOI)001092493900004 ()
Available from: 2023-12-13 Created: 2023-12-13 Last updated: 2023-12-13Bibliographically approved
Boldu O Farrill Treviño, J. J., Graham, D. B., Khotyaintsev, Y. V., Morooka, M., André, M., Dimmock, A. P., . . . Maksimovic, M. (2023). Ion-acoustic waves associated with interplanetary shocks.
Open this publication in new window or tab >>Ion-acoustic waves associated with interplanetary shocks
Show others...
2023 (English)In: Article in journal (Other academic) Submitted
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-516736 (URN)
Available from: 2023-11-28 Created: 2023-11-28 Last updated: 2023-11-28
Hadid, L. Z., Shebanits, O., Wahlund, J.-E., Morooka, M., Nagy, A. F., Farrell, W. M., . . . Ye, S.-Y. (2022). Ambipolar electrostatic field in negatively charged dusty plasma. Journal of Plasma Physics, 88(2), Article ID 555880201.
Open this publication in new window or tab >>Ambipolar electrostatic field in negatively charged dusty plasma
Show others...
2022 (English)In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 88, no 2, article id 555880201Article in journal (Refereed) Published
Abstract [en]

We study the effect of negatively charged dust on the magnetic-field-aligned polarisation electrostatic field (E-parallel to) using Cassini's RPWS/LP in situ measurements during the `ring-grazing' orbits. We derive a general expression for E-parallel to and estimate for the first time in situ parallel to E-parallel to parallel to (approximately 10(-5) V m(-1)) near the Janus and Epimetheus rings. We further demonstrate that the presence of the negatively charged dust close to the ring plane (vertical bar Z vertical bar less than or similar to 0.11 R-s) amplifies parallel to E-parallel to parallel to by at least one order of magnitude and reverses its direction due to the effect of the charged dust gravitational and inertial forces. Such reversal confines the electrons at the magnetic equator within the dusty region, around 0.047 R-s above the ring plane. Furthermore, we discuss the role of the collision terms, in particular the ion-dust drag force, in amplifying E-parallel to. These results imply that the charged dust, as small as nanometres in size, can have a significant influence on the plasma transport, in particular ambipolar diffusion along the magnetic field lines, and so their presence must be taken into account when studying such dynamical processes.

Place, publisher, year, edition, pages
Cambridge University Press, 2022
Keywords
dusty plasmas, space plasma physics, astrophysical plasmas
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-471686 (URN)10.1017/S0022377822000186 (DOI)000772006200001 ()
Available from: 2022-04-04 Created: 2022-04-04 Last updated: 2022-04-04Bibliographically approved
Vigren, E., Dreyer, J., Eriksson, A. I., Johansson, F. L., Morooka, M. & Wahlund, J.-E. (2022). Empirical Photochemical Modeling of Saturn's Ionization Balance Including Grain Charging. The Planetary Science Journal, 3(2), Article ID 49.
Open this publication in new window or tab >>Empirical Photochemical Modeling of Saturn's Ionization Balance Including Grain Charging
Show others...
2022 (English)In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 3, no 2, article id 49Article in journal (Refereed) Published
Abstract [en]

We present a semianalytical photochemical model of Saturn's near-equatorial ionosphere and adapt it to two regions (similar to 2200 and similar to 1700 km above the 1 bar level) probed during the inbound portion of Cassini's orbit 292 (2017 September 9). The model uses as input the measured concentrations of molecular hydrogen, hydrogen ion species, and free electrons, as well as the measured electron temperature. The output includes upper limits, or constraints, on the mixing ratios of two families of molecules, on ion concentrations, and on the attachment rates of electrons and ions onto dust grains. The model suggests mixing ratios of the two molecular families that, particularly near similar to 1700 km, differ notably from what independent measurements by the Ion Neutral Mass Spectrometer suggest. Possibly connected to this, the model suggests an electron-depleted plasma with a level of electron depletion of around 50%. This is in qualitative agreement with interpretations of Radio Plasma Wave Science/Langmuir Probe measurements, but an additional conundrum arises in the fact that a coherent photochemical equilibrium scenario then relies on a dust component with typical grain radii smaller than 3 angstrom.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2022
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-495353 (URN)10.3847/PSJ/ac4eee (DOI)000911845800001 ()
Funder
Swedish National Space Board
Available from: 2023-01-30 Created: 2023-01-30 Last updated: 2023-10-03Bibliographically approved
Sulaiman, A. H., Achilleos, N., Bertucci, C., Coates, A., Dougherty, M., Hadid, L., . . . Waite, J. H. (2022). Enceladus and Titan: emerging worlds of the Solar System. Experimental astronomy, 54(2-3), 849-876
Open this publication in new window or tab >>Enceladus and Titan: emerging worlds of the Solar System
Show others...
2022 (English)In: Experimental astronomy, ISSN 0922-6435, E-ISSN 1572-9508, Vol. 54, no 2-3, p. 849-876Article in journal (Refereed) Published
Abstract [en]

Some of the major discoveries of the recent Cassini-Huygens mission have put Titan and Enceladus firmly on the Solar System map. The mission has revolutionised our view of Solar System satellites, arguably matching their scientific importance with that of their host planet. While Cassini-Huygens has made big surprises in revealing Titan's organically rich environment and Enceladus' cryovolcanism, the mission's success naturally leads us to further probe these findings. We advocate the acknowledgement of Titan and Enceladus science as highly relevant to ESA's long-term roadmap, as logical follow-on to Cassini-Huygens. In this White Paper, we will outline important science questions regarding these satellites and identify the science themes we recommend ESA cover during the Voyage 2050 planning cycle. Addressing these science themes would make major advancements to the present knowledge we have about the Solar System, its formation, evolution, and likelihood that other habitable environments exist outside the Earth's biosphere.

Place, publisher, year, edition, pages
Springer Nature, 2022
Keywords
Titan, Enceladus, Voyage 2050
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:uu:diva-502312 (URN)10.1007/s10686-021-09810-z (DOI)000724648600001 ()
Available from: 2023-05-24 Created: 2023-05-24 Last updated: 2024-01-17Bibliographically approved
Dreyer, J., Vigren, E., Johansson, F., Shebanits, O., Morooka, M., Wahlund, J.-E., . . . Waite, J. H. (2022). Identifying Shadowing Signatures of C Ring Ringlets and Plateaus in Cassini Data from Saturn's Ionosphere. The Planetary Science Journal, 3(7), Article ID 168.
Open this publication in new window or tab >>Identifying Shadowing Signatures of C Ring Ringlets and Plateaus in Cassini Data from Saturn's Ionosphere
Show others...
2022 (English)In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 3, no 7, article id 168Article in journal (Refereed) Published
Abstract [en]

For orbits 288 and 292 of Cassini's Grand Finale, clear dips (sharp and narrow decreases) are visible in the H-2(+) densities measured by the Ion and Neutral Mass Spectrometer (INMS). In 2017, the southern hemisphere of Saturn was shadowed by its rings and the substructures within. Tracing a path of the solar photons through the ring plane to Cassini's position, we can identify regions in the ionosphere that were shadowed by the individual ringlets and plateaus (with increased optical depths) of Saturn's C ring. The calculated shadowed altitudes along Cassini's trajectory line up well with the dips in the H-2(+) data when adjusting the latter based on a detected evolving shift in the INMS timestamps since 2013, illustrating the potential for verification of instrument timings. We can further estimate the mean optical depths of the ringlets/plateaus by comparing the dips to inbound H-2(+) densities. Our results agree well with values derived from stellar occultation measurements. No clear dips are visible for orbits 283 and 287, whose periapsides were at higher altitudes. This can be attributed to the much longer chemical lifetime of H2+ at these higher altitudes, which in turn can be further used to estimate a lower limit for the flow speed along Cassini's trajectory. The resulting estimate of similar to 0.3 km s(-1) at an altitude of similar to 3400 km is in line with prior suggestions. Finally, the ringlet and plateau shadows are not associated with obvious dips in the electron density, which is expected due to their comparatively long chemical (recombination) lifetime.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2022
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-497057 (URN)10.3847/PSJ/ac7790 (DOI)000914478200001 ()
Funder
Swedish National Space Board, 143/18E. och K.G. Lennanders StipendiestiftelseSwedish National Space Board, Dnr 195/20
Available from: 2023-02-23 Created: 2023-02-23 Last updated: 2023-10-03Bibliographically approved
Vigren, E., Eriksson, A. I., Johansson, F. L., Marschall, R., Morooka, M. & Rubin, M. (2021). A Case for a Small to Negligible Influence of Dust Charging on the Ionization Balance in the Coma of Comet 67P. The Planetary Science Journal, 2(4), Article ID 156.
Open this publication in new window or tab >>A Case for a Small to Negligible Influence of Dust Charging on the Ionization Balance in the Coma of Comet 67P
Show others...
2021 (English)In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 2, no 4, article id 156Article in journal (Refereed) Published
Abstract [en]

A recent work aided by Rosetta in situ measurements set constraints on the dust-to-gas mass emission ratio and the size distribution of dust escaping the nucleus of comet 67P/Churyumov-Gerasimenko near perihelion. Here we use this information along with other observables/parameters as input into an analytical model aimed at estimating the number density of electrons attached to dust particles near the position of Rosetta. These theoretical estimates are compared to in situ measurements of the degree of ionization. The comparison proposes that Rosetta, while near perihelion, was typically not in electron-depleted regions of the inner coma of 67P. Our work suggests a typical level of electron depletion probably below 10% and possibly below 1%. In line with previous studies, we find, again with certain assumptions and other observables/parameters as input, that the observed negative spacecraft charging to a few tens of volts does not significantly impact the detection of charged dust grains, with a possible exception for grains with radii less than similar to 10 nm.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2021
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:uu:diva-497011 (URN)10.3847/PSJ/ac134f (DOI)000912770700001 ()
Funder
Swedish National Space Board, 168/15The European Space Agency (ESA), 4000118957/16/ES/JD
Available from: 2023-02-24 Created: 2023-02-24 Last updated: 2023-02-24Bibliographically approved
Holmberg, M. K., Cipriani, F., Nilsson, T., Hess, S., Huybrighs, H. L., Hadid, L. Z., . . . Felici, M. (2021). Cassini-Plasma Interaction Simulations Revealing the Cassini Ion Wake Characteristics: Implications for In-Situ Data Analyses and Ion Temperature Estimates. Journal of Geophysical Research - Space Physics, 126(8), Article ID e2020JA029026.
Open this publication in new window or tab >>Cassini-Plasma Interaction Simulations Revealing the Cassini Ion Wake Characteristics: Implications for In-Situ Data Analyses and Ion Temperature Estimates
Show others...
2021 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 126, no 8, article id e2020JA029026Article in journal (Refereed) Published
Abstract [en]

We have used Spacecraft Plasma Interaction Software (SPIS) simulations to study the characteristics (i.e., dimensions, ion depletion, and evolution with the changing spacecraft attitude) of the Cassini ion wake. We focus on two regions, the plasma disk at 4.5-€“4.7 RS, where the most prominent wake structure will be formed, and at 7.6 RS, close to the maximum distance at which a wake structure can be detected in the Cassini Langmuir probe (LP) data. This study also reveals how the ion wake and the spacecraft plasma interaction have impacted the Cassini LP measurements in the studied environments, for example, with a strong decrease in the measured ion density but with minor interference from the photoelectrons and secondary electrons originating from the spacecraft. The simulated ion densities and spacecraft potentials are in very good agreement with the LP measurements. This shows that SPIS is an excellent tool to use for analyses of LP data, when spacecraft material properties and environmental parameters are known and used correctly. The simulation results are also used to put constraints on the ion temperature estimates in the inner magnetosphere of Saturn. The best agreement between the simulated and measured ion density is obtained using an ion temperature of 8 eV at ∼4.6 RS. This study also shows that SPIS simulations can be used in order to better constrain plasma parameters in regions where accurate measurements are not available.

Place, publisher, year, edition, pages
American Geophysical Union (AGU)American Geophysical Union (AGU), 2021
Keywords
Cassini, ion density and temperature, ion wake, Langmuir probe, Saturn's magnetosphere, spacecraft charging
National Category
Fusion, Plasma and Space Physics
Research subject
Astronomy
Identifiers
urn:nbn:se:uu:diva-450200 (URN)10.1029/2020JA029026 (DOI)000691018000013 ()
Available from: 2021-08-13 Created: 2021-08-13 Last updated: 2024-01-15Bibliographically approved
Dreyer, J., Vigren, E., Morooka, M., Wahlund, J.-E., Buchert, S. C., Johansson, F. L. & Waite, J. H. (2021). Constraining the Positive Ion Composition in Saturn's Lower Ionosphere with the Effective Recombination Coefficient. The Planetary Science Journal, 2(1), Article ID 39.
Open this publication in new window or tab >>Constraining the Positive Ion Composition in Saturn's Lower Ionosphere with the Effective Recombination Coefficient
Show others...
2021 (English)In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 2, no 1, article id 39Article in journal (Refereed) Published
Abstract [en]

The present study combines Radio and Plasma Wave Science/Langmuir Probe and Ion and Neutral Mass Spectrometer data from Cassini's last four orbits into Saturn's lower ionosphere to constrain the effective recombination coefficient α300 from measured number densities and electron temperatures at a reference electron temperature of 300 K. Previous studies have shown an influx of ring material causes a state of electron depletion due to grain charging, which will subsequently affect the ionospheric chemistry. The requirement to take grain charging into account limits the derivation of α300 to upper limits. Assuming photochemical equilibrium and using an established method to calculate the electron production rate, we derive upper limits for α300 of ≲ 3 × 10−7 cm3 s−1 for altitudes below 2000 km. This suggests that Saturn's ionospheric positive ions are dominated by species with low recombination rate coefficients like HCO+. An ionosphere dominated by water group ions or complex hydrocarbons, as previously suggested, is incompatible with this result, as these species have recombination rate coefficients > 5 × 10−7 cm3 s−1 at an electron temperature of 300 K.

Place, publisher, year, edition, pages
American Astronomical SocietyAmerican Astronomical Society, 2021
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-458301 (URN)10.3847/psj/abd6e9 (DOI)000912867900001 ()
Funder
Swedish National Space Board, 143/18Swedish National Space Board, 168/15
Available from: 2021-11-08 Created: 2021-11-08 Last updated: 2024-01-15Bibliographically approved
Zaslavsky, A., Mann, I., Soucek, J., Czechowski, A., Pisa, D., Vaverka, J., . . . Vaivads, A. (2021). First dust measurements with the Solar Orbiter Radio and Plasma Wave instrument. Astronomy and Astrophysics, 656, Article ID A30.
Open this publication in new window or tab >>First dust measurements with the Solar Orbiter Radio and Plasma Wave instrument
Show others...
2021 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 656, article id A30Article in journal (Refereed) Published
Abstract [en]

Context. Impacts of dust grains on spacecraft are known to produce typical impulsive signals in the voltage waveform recorded at the terminals of electric antennas. Such signals (as may be expected) are routinely detected by the Time Domain Sampler (TDS) system of the Radio and Plasma Waves (RPW) instrument on board Solar Orbiter.

Aims. We investigate the capabilities of RPW in terms of interplanetary dust studies and present the first analysis of dust impacts recorded by this instrument. Our purpose is to characterize the dust population observed in terms of size, flux, and velocity.

Methods. We briefly discuss previously developed models of voltage pulse generation after a dust impact onto a spacecraft and present the relevant technical parameters for Solar Orbiter RPW as a dust detector. Then we present the statistical analysis of the dust impacts recorded by RPW /TDS from April 20, 2020 to February 27, 2021 between 0.5AU and 1AU.

Results. The study of the dust impact rate along Solar Orbiter's orbit shows that the dust population studied presents a radial velocity component directed outward from the Sun. Its order of magnitude can be roughly estimated as nu(r,dust) similar or equal to 50 km s(-1), which is consistent with the flux of impactors being dominated by fi-meteoroids. We estimate the cumulative flux of these grains at 1AU to be roughly F-beta similar or equal to 8 x 10(-5) m(-2) s(-1) for particles of a radius r greater than or similar to 100 nm. The power law index ffi of the cumulative mass flux of the impactors is evaluated by two di fferents methods, namely: direct observations of voltage pulses and indirect e ffect on the impact rate dependency on the impact speed. Both methods give the following result: delta similar or equal to 0.3-0.4.

Conclusions. Solar Orbiter RPW proves to be a suitable instrument for interplanetary dust studies, and the dust detection algorithm implemented in the TDS subsystem an e fficient tool for fluxes estimation. These first results are promising for the continuation of the mission, in particular, for the in situ study of the inner Solar System dust cloud outside of the ecliptic plane, which Solar Orbiter will be the first spacecraft to explore.

Place, publisher, year, edition, pages
EDP SciencesEDP Sciences, 2021
Keywords
instrumentation: detectors, methods: data analysis, meteorites, meteors, meteoroids, interplanetary medium
National Category
Fusion, Plasma and Space Physics Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:uu:diva-464266 (URN)10.1051/0004-6361/202140969 (DOI)000730246400045 ()
Funder
Swedish National Space Board, 20/136Swedish National Space Board
Available from: 2022-01-19 Created: 2022-01-19 Last updated: 2024-01-15Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9958-0241

Search in DiVA

Show all publications