Ion Heating and Magnetotail Losses at the Martian Ionosphere-Magnetosphere Interface

Abstract:

The Suprathermal And Thermal Ion Composition (STATIC) sensor on the MAVEN spacecraft provides the first detailed look at the heating of Martian ions at the interface between the ionosphere and the solar wind. STATIC’s unique design allows it to measure both a wide range in energy (<1 eV to 30,000 eV) and a large dynamic range in flux. At this interface ion distributions can be quite complex, with multiple ion species containing both cold plasmas (Ti < 0.1 eV) and warm suprathermal tails (1-100 eV). Ion heating at boundaries between different magnetic topologies, both open-closed and open-draped boundaries, is observed. Counterstreaming ions of the same mass, and of different masses, are common at this interface. These unstable distributions should evolve into low energy suprathermal tails that populate the magnetotail and contribute to Martian atmospheric loss. This paper will review the broad range of ion distributions that MAVEN observes escaping down the magnetotail beginning with outflows at the low altitude terminator and their evolution to a warm plasma that forms the tail current sheet. These observations will be used to estimate the atmospheric loss rate of tail outflows.