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withers

HR: 1340h
AN: SA13A-1874 Poster
TI: Hydrogen Species in the Ionosphere of Mars
AU: *Matta, M M
EM: majdm@bu.edu
AF: Astronomy Department, Boston University, Boston, MA, USA
AU: Lollo, A
EM: alollo@bu.edu
AF: Center for Space Physics, Boston University, Boston, MA, USA
AU: Withers, P
EM: withers@bu.edu
AF: Astronomy Department, Boston University, Boston, MA, USA
AU: Mendillo, M
EM: mendillo@bu.edu
AF: Astronomy Department, Boston University, Boston, MA, USA
AB: To date, there are only two in situ measurements of the composition of the neutral atmosphere and ionosphere of Mars, those made by the Viking 1 and Viking 2 Landers. On the other hand, models of the Martian ionosphere are plentiful, and most of these models use atmospheric chemistry that is aimed at reproducing the Viking measurements. In these modeling efforts, the atmospheric and ionospheric region of interest centers on the altitudes of the Viking measurements: between ~100 km to ~250 km. The main neutral species detected by Viking were: CO₂, N₂, Ar, CO, O₂, and NO. Atomic Oxygen densities were then inferred from chemical models and only trace detections of atomic and molecular hydrogen were found. Remote spectral measurements later found both H and H₂ to dominate the atmosphere above ~250 km. In the work presented here, we build a 1-D ionospheric model that ranges in altitude between 80 and 400 km and includes CO₂, CO, O, N₂, H₂ and H as neutral species. These species are then ionized to produce the primary ions CO₂⁺, CO⁺, O⁺, N₂⁺, H₂⁺ and H⁺. Further reactions with neutrals give rise to the secondary ions: O₂⁺, NO⁺, OH⁺, H₃⁺ and HCO⁺. We allow for two extreme cases of ambipolar diffusion to encompass the effects of induced or crustal magnetic field (B) morphologies: (1) horizontal-B and (2) vertical-B. The first case allows no vertical diffusion in the 1-D model and the second case allows for only vertical diffusion. We find that in the case of no vertical diffusion, the secondary ions HCO⁺, H₃⁺ and OH⁺ dominate the topside ionosphere along with O₂⁺. In the case of only vertical diffusion, we find that both HCO⁺ and O₂⁺ co-dominate the ionosphere. We discuss the implications of these predictions for MAVEN NGIMS observations.
DE: [2419] IONOSPHERE / Ion chemistry and composition
DE: [6225] PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS / Mars
SC: SPA-Aeronomy (SA)
MN: 2011 Fall Meeting