Hot carbon corona in Mars’ upper thermosphere and exosphere: 1. Mechanisms and structure of the hot corona for low solar activity at equinox

Abstract

Two important source reactions for hot atomic carbon on Mars are photodissociation of CO and dissociative recombination of CO + ; both reactions are highly sensitive to solar activity and occur mostly deep in the dayside thermosphere. The production of energetic particles results in the formation of hot coronae that are made up of neutral atoms including hot carbon. Some of these atoms are on ballistic trajectories and return to the thermosphere, and others escape. Understanding the physics in this region requires modeling that captures the complicated dynamics of hot atoms in 3-D. This study evaluates the carbon atom inventory by investigating the production and distribution of energetic carbon atoms using the full 3-D atmospheric input. The methodology and details of the hot atomic carbon model calculation are given, and the calculated total global escape of hot carbon from the assumed dominant photochemical processes at a fixed condition, equinox (L s = 180°), and low solar activity (F10.7 = 70 at Earth) are presented. To investigate the dynamics of these energetic neutral atoms, we have coupled a self-consistent 3-D global kinetic model, the Adaptive Mesh Particle Simulator, with a 3-D thermosphere/ionosphere model, the Mars Thermosphere General Circulation Model to provide a self-consistent global description of the hot carbon corona in the upper thermosphere and exosphere. The spatial distributions of density and temperature and atmospheric loss are simulated for the case considered.

Solar wind interaction with the Martian upper atmosphere: Crustal field orientation, solar cycle, and seasonal variations

“…In this section, we will briefly introduce the Mars Global Ionosphere Thermosphere Model (M-GITM) [Bougher et al, 2015], the Mars exosphere Monte Carlo model Adaptive Mesh Particle Simulator (M-AMPS) [Lee et al, 2013[Lee et al, , 2014a[Lee et al, , 2014b, and the 3-D BATS-R-US Mars multifluid MHD (MF-MHD) model [Najib et al, 2011;Dong et al, 2014]. All these models are being used to generate a model library of simulated outputs for the MAVEN mission (2014)(2015)(2016).…”

“…Besides, the sputtering caused by pickup ion (e.g., O + ) collisions with the Martian atmospheric neutral species is also an important source for the hot corona [Johnson and Luhmann, 1998]. There are hot hydrogen and carbon coronae as well [Lee et al, 2014a].…”

“…In order to reproduce a realistic asymmetric corona of hot species from observations, a 3-D global kinetic exosphere model is required, especially above the exobase (Knudsen number, K n ≈ 1) where the fluid assumption usually fails [Lee et al, 2013]. One such model is the Mars exosphere Monte Carlo model Adaptive Mesh Particle Simulator (M-AMPS) [Tenishev and Combi, 2008;Lee et al, 2013Lee et al, , 2014aLee et al, , 2014b, which can generate a 3-D hot (e.g., oxygen and carbon) corona with detailed asymmetric structure. In order to capture these 3-D asymmetries, 3-D thermosphere/ionosphere inputs from a validated ground-to-exobase atmospheric model (e.g., M-GITM) are essential (see Figure 1 for more detail).…”

“…Here we focus on the one-way coupling indicated by the solid line. For the detailed study of one-way coupling between M-GITM and M-AMPS (dashed line), please refer to Lee et al [2013Lee et al [ , 2014aLee et al [ , 2014b.…”

“…The MF-MHD code solves separate continuity, momentum, and energy equations for each ion species [Powell et al, 1999;Glocer et al, 2009;Najib et al, 2011;Tóth et al, 2012;Dong et al, 2014]. Please refer to Lee et al [2013Lee et al [ , 2014aLee et al [ , 2014b for the detailed study of one-way coupling between M-GITM and M-AMPS (as indicated by the dashed line in Figure 1); i.e., M-GITM provides thermosphere/ionosphere background as an input into the M-AMPS exosphere model. These calculations are carried out for 22 cases with combinations of different crustal field orientations (four cases without crustal field), solar cycle, and Martian seasonal conditions.…”