Pinpointing Production: A Particle Tracking Simulator Identifies Source Regions of Escaping Planetary O+

Abstract:

As observations of current Martian atmospheric erosion rates become increasingly precise, a complete understanding of the time evolution of the Martian atmosphere will be limited not by incomplete knowledge of current loss rates, but by an incomplete understanding of how this loss rate changes over time. Making progress on this front necessarily requires detailed understanding of the various acceleration mechanisms that lead to escape. With this in mind, we note that one open question which cannot be answered by in situ measurements of escaping ions is the altitude from which these escaping ions originate. A 3-D kinetic model, the Adaptive Mesh Particle Simulator (AMPS), is used to track oxygen ions from their source. AMPS takes collisions into account, allowing for the examination of the entire upper atmosphere, from beneath the ionospheric peak, through the transition region in which collisions become rare, all the way out to several Mars radii, making AMPS an effective tool for studying the source regions associated with the escape of O⁺ from the atmosphere of Mars.