MAVEN Case Studies of Plasma Dynamics in Low-Altitude Crustal Magnetic Field at Mars 1: Dayside Ion Spikes Associated With Radial Crustal Magnetic Fields - Archive ouverte HAL Access content directly
Journal Articles Journal of Geophysical Research: Space Physics Year : 2019

MAVEN Case Studies of Plasma Dynamics in Low-Altitude Crustal Magnetic Field at Mars 1: Dayside Ion Spikes Associated With Radial Crustal Magnetic Fields

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1
Y. I. J. Soobiah
  • Function : Author
Jared R. Espley
  • Function : Author
John E. P. Connerney
  • Function : Author
Jacob R. Gruesbeck
  • Function : Author
Gina A. Dibraccio
  • Function : Author
Jasper Halekas
Laila Andersson
  • Function : Author
Christopher M. Fowler
  • Function : Author
Robert J. Lillis
  • Function : Author
David L. Mitchell
  • Function : Author
Yuki Harada
  • Function : Author
Takuya Hara
  • Function : Author
Glyn Collinson
  • Function : Author
David Brain
Shaosui Xu
  • Function : Author
Shannon M. Curry
  • Function : Author
James P. Mcfadden
  • Function : Author
Mehdi Benna
Bruce M. Jakosky
  • Function : Author

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.
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insu-03674458 , version 1 (20-05-2022)

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Y. I. J. Soobiah, Jared R. Espley, John E. P. Connerney, Jacob R. Gruesbeck, Gina A. Dibraccio, et al.. 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, 2019, 124, pp.1239-1261. ⟨10.1029/2018JA025569⟩. ⟨insu-03674458⟩
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