Two Types of Martian Magnetotail Current Sheets: MAVEN Observations of Ion Composition

Abstract

Abstract Using measurements from the Mars Atmosphere and Volatile EvolutioN mission, we investigate the densities of H+ (nH+), O+ (nO+), and O2+ (no2+), respectively, in the Martian magnetotail current sheet. We find that the current sheet when it is closer to the terminator than 0.75 Mars radii is mostly dominated by heavy ions ((nO++no2+)>2 nH+), regardless of the variation of the upstream solar wind, but that it is sometimes dominated by H+ (nH+ >2(nO++no2+)) at downstream distances exceeding 0.75 Mars radii. The occurrence rate of the dominant H+ weakly increases (and that of the heavy ions decreases) with solar wind density and dynamic pressure. Our results suggest that solar wind protons could enter the Martian tail and may become the dominant ion species in the current sheet, particularly when the solar wind density or dynamic pressure is high.

Keywords

• Martian magnetotail current sheet
• current sheet
• ion composition
• ion density
• ion species
• ion escape