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Nightside ionosphere of Mars: Composition, vertical structure, and variability
- Source :
- Journal of Geophysical Research - Space Physics; April 2017, Vol. 122 Issue: 4 p4712-4725, 14p
- Publication Year :
- 2017
-
Abstract
- We provide an overview of the composition, vertical structure, and variability of the nightside ionosphere of Mars as observed by Mars Atmosphere and Volatile EvolutioN (MAVEN)'s Neutral Gas and Ion Mass Spectrometer (NGIMS) through 19 months of the MAVEN mission. We show that O 2+is the most abundant ion down to ∼130 km at all nightside solar zenith angles (SZA). However, below 130 km NO+is the most abundant ion, and NO+densities increase with decreasing altitude down to at least 120 km. We also show how the densities of the major ions decrease with SZA across the terminator. At lower altitudes the O 2+and CO 2+densities decrease more rapidly with SZA than the NO+and HCO+densities, which changes the composition of the ionosphere from being primarily O 2+on the dayside to being a mixture of O 2+, NO+, and HCO+on the nightside. These variations are in accord with the expected ion‐neutral chemistry, because both NO+and HCO+have long chemical lifetimes. Additionally, we present median ion density profiles from three different nightside SZA ranges, including deep on the nightside at SZAs greater than 150° and discuss how they compare to particle precipitation models. Finally, we show that nightside ion densities can vary by nearly an order of magnitude over monthlong timescales. The largest nightside densities were observed at high northern latitudes during winter and coincided with a major solar energetic particle event. The composition of the nightside ionosphere of Mars is characterizedO 2+is the major nightside ion down to 130 km, below which NO+becomes the major ionNightside ion densities can vary by nearly an order of magnitude over monthlong timescales
Details
- Language :
- English
- ISSN :
- 21699380 and 21699402
- Volume :
- 122
- Issue :
- 4
- Database :
- Supplemental Index
- Journal :
- Journal of Geophysical Research - Space Physics
- Publication Type :
- Periodical
- Accession number :
- ejs42512984
- Full Text :
- https://doi.org/10.1002/2016JA023508