Journal article
Statistical analysis of the reflection of incident O+ pickup ions at Mars: MAVEN observations
Journal of geophysical research. Space physics, Vol.122(4), pp.4089-4101
04/2017
DOI: 10.1002/2016JA023516
Abstract
Analyzing ~1.3 year data set of O+ ion velocity distribution functions obtained from the Suprathermal and Thermal Ion Composition instrument on the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, we statistically investigate reflections of incident O+ pickup ions (>10 keV) occurring below the Martian bow shock. To quantitatively evaluate importance of the reflection of incident O+ pickup ions, we estimate reflection ratios by calculating average inward and outward O+ ion fluxes above the Martian bow shock. Our result shows that an average reflection ratio is 14.1 ± 6.7%. We also investigate dependences of the reflection ratio on the solar wind, solar EUV flux, and southern hemispheric crustal magnetic field on Mars. We find that the reflection ratio strongly depends on the magnitude of the interplanetary magnetic field (IMF), solar wind dynamic pressure, and gyroradius of O+ pickup ions in the solar wind, rather than the solar EUV flux and the crustal magnetic field. We suggest that the reflection ratio is determined by the magnetic field both in the solar wind and below the bow shock that mainly controls gyroradius of incident O+ pickup ions in these regions. We also find that the reflection ratio increases to 38.9 ± 10.2% as these parameters become extreme conditions (i.e., IMF magnitude >6 nT). Since incident O+ pickup ions are known to be a major source of atmospheric sputtering escape from Mars, our result suggests that ion reflections may have a role to reduce the sputtering escape from Mars under the extreme solar wind condition.
Key Points
Average reflection ratio of incident O+ pickup ions from the Martian magnetosheath/magnetic pileup region is ~14%
The reflection ratio reaches ~39% under extreme solar wind conditions
The reflection ratio is determined by magnetic fields both in the solar wind and below the bow shock
Details
- Title: Subtitle
- Statistical analysis of the reflection of incident O+ pickup ions at Mars: MAVEN observations
- Creators
- K Masunaga - The University of TokyoK Seki - The University of TokyoD. A Brain - University of Colorado BoulderX Fang - University of Colorado BoulderY Dong - University of Colorado BoulderB. M Jakosky - University of Colorado BoulderJ. P McFadden - University of California, BerkeleyJ. S Halekas - University of IowaJ. E. P Connerney - Goddard Space Flight CenterD. L Mitchell - University of California, BerkeleyF. G Eparvier - University of Colorado Boulder
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.122(4), pp.4089-4101
- DOI
- 10.1002/2016JA023516
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Number of pages
- 13
- Grant note
- Program for Advancing Strategic International Networks to Accelerate the Circulation of Talented Researchers G2602 and Grant‐in‐Aid for Scientific Research (B) (15H0731) JSPS Fellows (14J03613)
- Language
- English
- Date published
- 04/2017
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199803902771
Metrics
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