Change in Plasma Composition During the Rotation of the Magnetopause of Mars

Abstract—

High temporal resolution of measurements of the magnetic field and plasma of Mars is provided by observations on the Mars Atmosphere and Volatile Evolution (MAVEN; Jakosky et al., 2015) satellite, making it possible to analyze thin layers of the plasma envelope of Mars. This paper describes the magnetic structure associated with the daytime Martian magnetopause. It was shown that the solar wind passing through the shock wave on the dayside of Mars does not directly interact with the Martian ionosphere. A layer of plasma and magnetic field 200–300 km thick forms the daytime magnetosphere, which is the region between the magnetosheath and the ionosphere (Vaisberg and Shuvalov, 2020). There are two types of daytime magnetosphere: (1) the more common type of magnetosphere consists of heated and accelerated O⁺ ions and \({\text{O}}_{2}^{ + }\), located between the ionosphere and the flowing hot stream of Mars; (2) another type of daytime magnetosphere consists of accelerated O⁺ ions and \({\text{O}}_{2}^{ + }\) in the magnetosheath, where they form a continuing accelerated beam, forming a plume. Between the magnetosheath and the magnetosphere there is a magnetic structure that rotates, almost without changing its size. This structure is located in the second part of the n_p/(n_p + n_h) transition from ~1 to ~10^–2. The transition between the magnetosheath and magnetosphere occurs smoothly, both in energy density and in ion composition, with a decrease in the proton flux and an increase in the heavy ion flux.