Journal article
MAVEN measured oxygen and hydrogen pickup ions: Probing the Martian exosphere and neutral escape
Journal of geophysical research. Space physics, Vol.122(3), pp.3689-3706
03/2017
DOI: 10.1002/2016JA023371
Abstract
Soon after the MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft started orbiting Mars, the SEP (Solar Energetic Particle), SWIA (Solar Wind Ion Analyzer), and STATIC (Supra‐Thermal and Thermal Ion Composition) instruments on board the spacecraft detected planetary pickup ions. SEP can measure energetic (>60 keV) oxygen pickup ions, the source of which is the extended hot oxygen exosphere of Mars. Model results show that these pickup ions originate from tens of Martian radii upstream of Mars and are energized by the solar wind motional electric field as they gyrate back toward Mars. SWIA and STATIC can detect both pickup oxygen and pickup hydrogen with energies below ~30 keV and created closer to Mars. In this study, data from the SEP, SWIA, and STATIC instruments containing pickup ion signatures are provided and model‐data comparisons are shown. During the times when MAVEN is outside the Martian bow shock and in the upstream undisturbed solar wind, the solar wind velocity measured by SWIA and the solar wind (or interplanetary) magnetic field measured by the MAG (magnetometer) instrument can be used to model pickup oxygen and hydrogen fluxes. By comparing measured pickup ion fluxes with model results, the Martian thermal hydrogen and hot oxygen neutral densities can be probed outside the bow shock, providing a helpful tool in constraining estimates of neutral oxygen and hydrogen escape rates. Our analysis reveals an order of magnitude density change with Mars season in the hydrogen exosphere, whereas the hot oxygen exosphere was found to remain steadier.
Key Points
Model‐data comparisons of MAVEN SEP, SWIA, and STATIC measured oxygen and hydrogen pickup ions are presented
Three case studies demonstrate how pickup ion model‐data comparisons can constrain Mars exospheric neutral densities
Factor of 10 change with Mars season in the hydrogen exosphere is observed, whereas the oxygen exosphere remained steadier
Details
- Title: Subtitle
- MAVEN measured oxygen and hydrogen pickup ions: Probing the Martian exosphere and neutral escape
- Creators
- A Rahmati - University of California, BerkeleyD. E Larson - University of California, BerkeleyT. E Cravens - University of KansasR. J Lillis - University of California, BerkeleyJ. S Halekas - University of IowaJ. P McFadden - University of California, BerkeleyP. A Dunn - University of California, BerkeleyD. L Mitchell - University of California, BerkeleyE. M. B Thiemann - University of Colorado BoulderF. G Eparvier - University of Colorado BoulderG. A DiBraccio - Goddard Space Flight CenterJ. R Espley - Goddard Space Flight CenterC Mazelle - Centre National pour la Recherche Scientifique et Technique (CNRST)B. M Jakosky - University of Colorado Boulder
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.122(3), pp.3689-3706
- DOI
- 10.1002/2016JA023371
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Number of pages
- 18
- Grant note
- NASA NASA Postdoctoral Program
- Language
- English
- Date published
- 03/2017
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199739702771
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