Journal article
MAVEN Case Studies of Plasma Dynamics in Low‐Altitude Crustal Magnetic Field at Mars 1: Dayside Ion Spikes Associated With Radial Crustal Magnetic Fields
Journal of geophysical research. Space physics, Vol.124(2), pp.1239-1261
02/2019
DOI: 10.1029/2018JA025569
Abstract
We report for the first time, simultaneous ion, electron, magnetic field vector and electric field wave measurements made possible by Mars Atmosphere and Volatile EvolutioN, during ion energy flux spikes in low‐altitude radial crustal magnetic fields on the Mars dayside. Observations show energetic electrons and ions (E > 25 eV) precipitating on magnetic field lines assumed as closed. Ions (E < 1.4 keV) display broad velocity distributions toward Mars, showing ions flowing from higher altitude possibly after magnetic reconnection or loss cone filling from pitch angle scattering effects. Precipitating ions (E < 1.4 keV) show nonadiabatic features depending on ion mass and energy and returning ions (E < 1.4 keV) show evidence of conserving the first adiabatic invariant in a mirror field. We observe magnetic field perturbations up to 60 nT, electric field wave amplitudes up to 38 mV/m, and brief periods of peaked electron spectra. At ∼175 km and at times Mars Atmosphere and Volatile EvolutioN is below the mirroring altitude of electrons, we observe mirroring and transverse heating of H+ ions alongside increased electric field wave amplitude fluctuations. It suggests field aligned potential drops result from different mirror altitudes of ions and electrons. Ions E > 1.4 keV (O+) occur as injected accelerated ion beams and ions heated after energization or deceleration. Energy dispersed kilo‐electron‐volt ions suggest a selection effect in radial magnetic fields for lower‐energy Marsward ions, compared to reflection of higher‐energy anti‐Sunward ions. Precipitating kilo‐electron‐volt ions show energy deposition rates of 3.6 ×10−6 W/m2 and sputtering escape rates from precipitating O+ ions of 1.5 ×105/(cm2.s) and 2.1 ×106/(cm2.s) are calculated.
Plain Language Summary
Mars Atmosphere and Volatile EvolutioN arrived at Mars on 21 September 2014 to study the effects of the solar wind interaction on the upper atmosphere. This study reports the raining of both energetic electrons and multiple populations of ions at low altitudes and over regions of ancient magnetic field from the Martian crust. These observations are associated with large magnetic field deflections and large electric field fluctuations. The results are important for understanding plasma transport and associated electrodynamics where the crustal magnetic fields point vertically toward or away from the planet. Such analysis was not possible with previous missions, which did not include the complete set of space plasma instruments carried by Mars Atmosphere and Volatile EvolutioN. Some ions display behaviors not expected for the small curvature of the crustal magnetic fields; ions that are locally tied that would require much larger magnetic field structures or ions injected along the direction of the magnetic field. Oxygen ions that originate from Mars that have been picked up by the solar wind and moving at very high speeds are selected over regions of vertical magnetic field to travel directly toward the planet. These ions will have head on impacts with Mars to heat and blast atmosphere out into space.
Key Points
Investigated plasma transport and associated electrodynamics during ion energy flux spikes in radial crustal fields on the Mars dayside
Precipitating ion and electron energy flux spikes on closed field consisting of ion beams E > 1.4 keV and broad ion distributions E < 1.4 keV
Considered impact of low‐altitude precipitating O+ ions E > 25 eV on localized heating and atmospheric escape
Details
- Title: Subtitle
- MAVEN Case Studies of Plasma Dynamics in Low‐Altitude Crustal Magnetic Field at Mars 1: Dayside Ion Spikes Associated With Radial Crustal Magnetic Fields
- Creators
- Y. I. J. Soobiah - Goddard Space Flight CenterJared R. Espley - Goddard Space Flight CenterJohn E. P. Connerney - Goddard Space Flight CenterJacob R. Gruesbeck - Goddard Space Flight CenterGina A. DiBraccio - Goddard Space Flight CenterJasper Halekas - University of IowaLaila Andersson - Laboratory for Atmospheric and Space PhysicsChristopher M. Fowler - Laboratory for Atmospheric and Space PhysicsRobert J. Lillis - University of California, BerkeleyDavid L. Mitchell - University of CaliforniaChristian Mazelle - Université de ToulouseYuki Harada - Kyoto UniversityTakuya Hara - University of California, BerkeleyGlyn Collinson - Goddard Space Flight CenterDavid Brain - Laboratory for Atmospheric and Space PhysicsShaosui Xu - University of California, BerkeleyShannon M. Curry - University of California, BerkeleyJames P. Mcfadden - University of California, BerkeleyMehdi Benna - Goddard Space Flight CenterBruce M. Jakosky - Laboratory for Atmospheric and Space Physics
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.124(2), pp.1239-1261
- DOI
- 10.1029/2018JA025569
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Number of pages
- 23
- Language
- English
- Date published
- 02/2019
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984428784302771
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