| 1. |
- Jakosky, B. M., et al.
(författare)
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MAVEN observations of the response of Mars to an interplanetary coronal mass ejection
- 2015
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 350:6261
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Tidskriftsartikel (refereegranskat)abstract
- Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ongoing ion loss to space, the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft made comprehensive measurements of the Mars upper atmosphere, ionosphere, and interactions with the Sun and solar wind during an interplanetary coronal mass ejection impact in March 2015. Responses include changes in the bow shock and magnetosheath, formation of widespread diffuse aurora, and enhancement of pick-up ions. Observations and models both show an enhancement in escape rate of ions to space during the event. Ion loss during solar events early in Mars history may have been a major contributor to the long-term evolution of the Mars atmosphere.
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| 2. |
- Goetz, C., et al.
(författare)
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Cometary plasma science : Open science questions for future space missions
- 2021
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Ingår i: Experimental astronomy. - : Springer Nature. - 0922-6435 .- 1572-9508.
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Tidskriftsartikel (refereegranskat)abstract
- Comets hold the key to the understanding of our Solar System, its formation and its evolution, and to the fundamental plasma processes at work both in it and beyond it. A comet nucleus emits gas as it is heated by the sunlight. The gas forms the coma, where it is ionised, becomes a plasma, and eventually interacts with the solar wind. Besides these neutral and ionised gases, the coma also contains dust grains, released from the comet nucleus. As a cometary atmosphere develops when the comet travels through the Solar System, large-scale structures, such as the plasma boundaries, develop and disappear, while at planets such large-scale structures are only accessible in their fully grown, quasi-steady state. In situ measurements at comets enable us to learn both how such large-scale structures are formed or reformed and how small-scale processes in the plasma affect the formation and properties of these large scale structures. Furthermore, a comet goes through a wide range of parameter regimes during its life cycle, where either collisional processes, involving neutrals and charged particles, or collisionless processes are at play, and might even compete in complicated transitional regimes. Thus a comet presents a unique opportunity to study this parameter space, from an asteroid-like to a Mars- and Venus-like interaction. The Rosetta mission and previous fast flybys of comets have together made many new discoveries, but the most important breakthroughs in the understanding of cometary plasmas are yet to come. The Comet Interceptor mission will provide a sample of multi-point measurements at a comet, setting the stage for a multi-spacecraft mission to accompany a comet on its journey through the Solar System. This White Paper, submitted in response to the European Space Agency’s Voyage 2050 call, reviews the present-day knowledge of cometary plasmas, discusses the many questions that remain unanswered, and outlines a multi-spacecraft European Space Agency mission to accompany a comet that will answer these questions by combining both multi-spacecraft observations and a rendezvous mission, and at the same time advance our understanding of fundamental plasma physics and its role in planetary systems.
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| 3. |
- Jakosky, B. M., et al.
(författare)
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The Mars Atmosphere and Volatile Evolution (MAVEN) Mission
- 2015
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Ingår i: Space Science Reviews. - : Springer Science and Business Media LLC. - 0038-6308 .- 1572-9672. ; 195:1-4, s. 3-48
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Forskningsöversikt (refereegranskat)abstract
- The MAVEN spacecraft launched in November 2013, arrived at Mars in September 2014, and completed commissioning and began its one-Earth-year primary science mission in November 2014. The orbiter's science objectives are to explore the interactions of the Sun and the solar wind with the Mars magnetosphere and upper atmosphere, to determine the structure of the upper atmosphere and ionosphere and the processes controlling it, to determine the escape rates from the upper atmosphere to space at the present epoch, and to measure properties that allow us to extrapolate these escape rates into the past to determine the total loss of atmospheric gas to space through time. These results will allow us to determine the importance of loss to space in changing the Mars climate and atmosphere through time, thereby providing important boundary conditions on the history of the habitability of Mars. The MAVEN spacecraft contains eight science instruments (with nine sensors) that measure the energy and particle input from the Sun into the Mars upper atmosphere, the response of the upper atmosphere to that input, and the resulting escape of gas to space. In addition, it contains an Electra relay that will allow it to relay commands and data between spacecraft on the surface and Earth.
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| 4. |
- Fowler, C. M., et al.
(författare)
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Electric and magnetic variations in the near-Mars environment
- 2017
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Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 122:8, s. 8536-8559
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Fowler, C. M., et al.
(författare)
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The first in situ electron temperature and density measurements of the Martian nightside ionosphere
- 2015
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 42:21, s. 8854-8861
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Rojo, M., et al.
(författare)
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Electron moments derived from the Mercury Electron Analyzer during the cruise phase of BepiColombo
- 2024
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 683
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We derive electron density and temperature from observations obtained by the Mercury Electron Analyzer on board Mio during the cruise phase of BepiColombo while the spacecraft is in a stacked configuration. Methods. In order to remove the secondary electron emission contribution, we first fit the core electron population of the solar wind with a Maxwellian distribution. We then subtract the resulting distribution from the complete electron spectrum, and suppress the residual count rates observed at low energies. Hence, our corrected count rates consist of the sum of the fitted Maxwellian core electron population with a contribution at higher energies. We finally estimate the electron density and temperature from the corrected count rates using a classical integration method. We illustrate the results of our derivation for two case studies, including the second Venus flyby of BepiColombo when the Solar Orbiter spacecraft was located nearby, and for a statistical study using observations obtained to date for distances to the Sun ranging from 0.3 to 0.9 AU. Results. When compared either to measurements of Solar Orbiter or to measurements obtained by HELIOS and Parker Solar Probe, our method leads to a good estimation of the electron density and temperature. Hence, despite the strong limitations arising from the stacked configuration of BepiColombo during its cruise phase, we illustrate how we can retrieve reasonable estimates for the electron density and temperature for timescales from days down to several seconds.
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| 7. |
- Rojo, M., et al.
(författare)
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Structure and dynamics of the Hermean magnetosphere revealed by electron observations from the Mercury electron analyzer after the first three Mercury flybys of BepiColombo
- 2024
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 687
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Tidskriftsartikel (refereegranskat)abstract
- Context: The Mercury electron analyzer (MEA) obtained new electron observations during the first three Mercury flybys by BepiColombo on October 1, 2021 (MFB1), June 23 , 2022 (MFB2), and June 19, 2023 (MFB3). BepiColombo entered the dusk side magnetotail from the flank magnetosheath in the northern hemisphere, crossed the Mercury solar orbital equator around midnight in the magnetotail, traveled from midnight to dawn in the southern hemisphere near the closest approach, and exited from the post-dawn magnetosphere into the dayside magnetosheath.Aims: We aim to identify the magnetospheric boundaries and describe the structure and dynamics of the electron populations observed in the various regions explored along the flyby trajectories.Methods: We derive 4s time resolution electron densities and temperatures from MEA observations. We compare and contrast our new BepiColombo electron observations with those obtained from the Mariner 10 scanning electron spectrometer (SES) 49 yr ago.Results: A comparison to the averaged magnetospheric boundary crossings of MESSENGER indicates that the magnetosphere of Mercury was compressed during MFB1, close to its average state during MFB2, and highly compressed during MFB3. Our new MEA observations reveal the presence of a wake effect very close behind Mercury when BepiColombo entered the shadow region, a significant dusk-dawn asymmetry in electron fluxes in the nightside magnetosphere, and strongly fluctuating electrons with energies above 100s eV in the dawnside magnetosphere. Magnetospheric electron densities and temperatures are in the range of 10-30 cm-3 and above a few 100s eV in the pre-midnight-sector, and in the range of 1-100 cm-3 and well below 100 eV in the post-midnight sector, respectively.Conclusions: The MEA electron observations of different solar wind properties encountered during the first three Mercury flybys reveal the highly dynamic response and variability of the solar wind-magnetosphere interactions at Mercury. A good match is found between the electron plasma parameters derived by MEA in the various regions of the Hermean environment and similar ones derived in a few cases from other instruments on board BepiColombo.
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| 8. |
- Trotignon, J. G., et al.
(författare)
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RPC-MIP : The mutual impedance probe of the Rosetta Plasma Consortium
- 2007
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Ingår i: Space Science Reviews. - : Springer Science and Business Media LLC. - 0038-6308 .- 1572-9672. ; 128:1-4, s. 713-728
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Forskningsöversikt (refereegranskat)abstract
- The main objective of the Mutual Impedance Probe (MIP), part of the Rosetta Plasma Consortium (RPC), is to measure the electron density and temperature of Comet 67P/Churyumov-Gerasimenko's coma, in particular inside the contact surface. Furthermore, MIP will determine the bulk velocity of the ionised outflowing atmosphere, define the spectral distribution of natural plasma waves, and monitor dust and gas activities around the nucleus. The MIP instrumentation consists of an electronics board for signal processing in the 7 kHz to 3.5 MHz range and a sensor unit of two receiving and two transmitting electrodes mounted on a 1-m long bar. In addition, the Langmuir probe of the RPC/LAP instrument that is at about 4 m from the MIP sensor can be used as a transmitter (in place of the MIP ones) and MIP as a receiver in order to have access to the density and temperature of plasmas at higher Debye lengths than those for which the MIP is originally designed.
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