Early MAVEN Deep Dip campaign reveals thermosphere and ionosphere variability

Bougher, S. W.; Jakosky, B. M.; Halekas, J. S.; Grebowsky, J. M.; Luhmann, J. G.; Mahaffy, P.; Connerney, J. E. P.; Eparvier, F.; Ergun, R. E.; Larson, D. E.; McFadden, J. P.; Mitchell, David; Schneider, Nicholas M.; Zurek, R. W.; Mazelle, C.; Andersson, L.; Andrews, David; Baird, Darren; Baker, D. N.; Bell, J. M.; Benna, M.; Brain, David; Chaffin, Michael; Chamberlin, Phillip C.; Chaufray, Jean‐Yves; Clarke, J. T.; Collinson, G.; Combi, M. R.; Crary, F. J.; Cravens, T. E.; Crismani, Matteo; Curry, S.; Curtis, D. W.; Deighan, Justin; Delory, G. T.; Dewey, R. M.; DiBraccio, G. A.; Dong, Chuanfei; Dong, Y.; Dunn, P.; Elrod, M. K.; England, S.; Eriksson, Anders; Espley, J. R.; Evans, Scott; Fang, Xiaohua; Fillingim, M. O.; Fortier, K.; Fowler, Christopher; Fox, Jane L.; Gröller, H.; Guzewich, Scott D.; Hara, Takuya; Harada, Yuki; Holsclaw, Gregory M.; Jain, Sonal; Jolitz, R.; Leblanc, François; Lee, C. O.; Lee, Y.; Lefèvre, Franck; Lillis, R. J.; Livi, R.; Lo, Daniel; Ma, Yingjuan; Mayyasi, Majd; McClintock, W. E.; McEnulty, T.; Modolo, Ronan; Montmessin, Franck; Morooka, M.; Nagy, Andrew F.; Olsen, Kirk; Peterson, W. K.; Rahmati, Ali; Ruhunusiri, S.; Russell, C. T.; Sakai, Shotaro; Sauvaud, J. A.; Seki, K.; Steckiewicz, M.; Stevens, M. H.; Stewart, A. I. F.; Stiepen, Arnaud; Stone, Shane; Tenishev, V.; Thiemann, E.; Tolson, R. H.; Toublanc, D.; Vogt, Marissa F.; Weber, Tristan; Withers, Paul; Woods, Thomas N.; Yelle, R. V.

doi:10.1126/science.aad0459

Cited by 98 publications

(119 citation statements)

References 38 publications

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“…Fortuitously, a portion of the solar wind charge exchanges with Martian exospheric constituents outside of the bow shock, converting it to energetic neutral atoms (ENAs) that do not feel electromagnetic fields and allowing them to penetrate to low altitudes in the atmosphere [ Kallio et al ., ; Kallio and Barabash , ]. Below ~250 km, some of these ENAs undergo electron stripping or electron attachment, converting them back to a charged form that we can measure [ Halekas et al ., ; Bougher et al ., ]. As described in Halekas et al .…”

Section: Solar Energy Inputs To the Martian Systemmentioning

confidence: 99%

Structure, dynamics, and seasonal variability of the Mars‐solar wind interaction: MAVEN Solar Wind Ion Analyzer in‐flight performance and science results

et al. 2017

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We report on the in‐flight performance of the Solar Wind Ion Analyzer (SWIA) and observations of the Mars‐solar wind interaction made during the Mars Atmosphere and Volatile EvolutioN (MAVEN) prime mission and a portion of its extended mission, covering 0.85 Martian years. We describe the data products returned by SWIA and discuss the proper handling of measurements made with different mechanical attenuator states and telemetry modes, and the effects of penetrating and scattered backgrounds, limited phase space coverage, and multi‐ion populations on SWIA observations. SWIA directly measures solar wind protons and alpha particles upstream from Mars. SWIA also provides proxy measurements of solar wind and neutral densities based on products of charge exchange between the solar wind and the hydrogen corona. Together, upstream and proxy observations provide a complete record of the solar wind experienced by Mars, enabling organization of the structure, dynamics, and ion escape from the magnetosphere. We observe an interaction that varies with season and solar wind conditions. Solar wind dynamic pressure, Mach number, and extreme ultraviolet flux all affect the bow shock location. We confirm the occurrence of order‐of‐magnitude seasonal variations of the hydrogen corona. We find that solar wind Alfvén waves, which provide an additional energy input to Mars, vary over the mission. At most times, only weak mass loading occurs upstream from the bow shock. However, during periods with near‐radial interplanetary magnetic fields, structures consistent with Short Large Amplitude Magnetic Structures and their wakes form upstream, dramatically reconfiguring the Martian bow shock and magnetosphere.

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Section: Solar Energy Inputs To the Martian Systemmentioning

confidence: 99%

Structure, dynamics, and seasonal variability of the Mars‐solar wind interaction: MAVEN Solar Wind Ion Analyzer in‐flight performance and science results

et al. 2017

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“…The periapsis is periodically lowered down to 125 km for five-day periods known as "deep-dips" (Bougher et al, 2015). Once the science mapping orbit has been reached, the Science phase began on 16 November 2014.…”

Section: Maven Instrumentsmentioning

confidence: 99%

Dawn/Dusk Asymmetry of the Martian UltraViolet Terminator Observed Through Suprathermal Electron Depletions

et al. 2019

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Suprathermal electron depletions are structures of the nightside ionosphere of Mars resulting from an equilibrium between electron loss and creation processes. Photoionization of oxygen and carbon dioxide by UV and EUV photons is the main ionization process of the Martian atmosphere. The observation of suprathermal electron depletions is strongly unexpected in the portion of the Martian environment where photoionization can occur. This region is delimited by the UltraViolet (UV) terminator, behind which no UV ionizing photons are detected. In this study suprathermal electron depletions are used to determine the position of the UV terminator thanks to MAVEN observations. The MAVEN spacecraft is now in its fourth year of data recording and has already covered more than one Martian year, a large range of latitude, local time, and solar zenith angle in the nightside down to 110‐km altitude. This coverage enables us to determine the approximate position of the UV terminator over one Martian year. We then investigate the variation of its position on the dawnside and duskside and depending on seasons. Our results are compared with models of the Martian atmosphere and in situ data of the atmospheric composition which all highlight an asymmetry between the duskside and the dawnside at equinox. However, models show an inversion in the position of the dusk and the dawn UV terminator at perihelion and aphelion, which cannot yet be confirmed or disproved by the data.

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“…The major neutral species in the thermosphere of Mars is CO 2 , although atomic oxygen is the major neutral species at higher altitudes (i.e., above about 200–250 km depending on solar activity level) [ Bougher et al ., , ; Mahaffy et al ., ]. Ions and photoelectrons are created on the dayside via photoionization of neutrals by solar EUV and soft X‐ray radiation:

\begin{matrix} left \\ h ν + {C O}_{2} \to {normalC normalO}_{2}^{+} + e \\ h ν + O \to {normalO}^{+} + e \end{matrix}

…”

Section: Ionospheric Chemistrymentioning

confidence: 99%

Hot oxygen escape from Mars: Simple scaling with solar EUV irradiance

et al. 2017

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The evolution of the atmosphere of Mars and the loss of volatiles over the lifetime of the solar system is a key topic in planetary science. An important loss process for atomic species, such as oxygen, is ionospheric photochemical escape. Dissociative recombination of O2+ ions (the major ion species) produces fast oxygen atoms, some of which can escape from the planet. Many theoretical hot O models have been constructed over the years, although a number of uncertainties are present in these models, particularly concerning the elastic cross sections of O atoms with CO2. Recently, the Mars Atmosphere and Volatile Evolution mission has been rapidly improving our understanding of the upper atmosphere and ionosphere of Mars and its interaction with the external environment (e.g., solar wind), allowing a new assessment of this important loss process. The purpose of the current paper is to take a simple analytical approach to the oxygen escape problem in order to (1) study the role that variations in solar radiation or solar wind fluxes could have on escape in a transparent fashion and (2) isolate the effects of uncertainties in oxygen cross sections on the derived oxygen escape rates. In agreement with several more elaborate numerical models, we find that the escape flux is directly proportional to the incident solar extreme ultraviolet irradiance and is inversely proportional to the backscatter elastic cross section. The amount of O lost due to ion transport in the topside ionosphere is found to be about 5–10% of the total.

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Early MAVEN Deep Dip campaign reveals thermosphere and ionosphere variability

Cited by 98 publications

References 38 publications

Structure, dynamics, and seasonal variability of the Mars‐solar wind interaction: MAVEN Solar Wind Ion Analyzer in‐flight performance and science results

Structure, dynamics, and seasonal variability of the Mars‐solar wind interaction: MAVEN Solar Wind Ion Analyzer in‐flight performance and science results

Dawn/Dusk Asymmetry of the Martian UltraViolet Terminator Observed Through Suprathermal Electron Depletions

Hot oxygen escape from Mars: Simple scaling with solar EUV irradiance

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