Structure of the Martian dayside magnetosphere: two types

TL;DR

This paper analyzes the structure and properties of Mars's dayside magnetosphere using MAVEN data, identifying two distinct plasma layer types and their formation conditions.

Contribution

It provides a detailed characterization of the two types of Mars's dayside magnetosphere and their formation mechanisms based on high-resolution MAVEN measurements.

Findings

Identification of two plasma layer types in Mars's dayside magnetosphere

Characterization of plasma populations and their properties

Analysis of conditions leading to the formation of each layer

Abstract

The comprehensive suite of scientific instruments with high temporal resolution measurements on the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft allowed studies of the structure and properties of the dayside magnetosphere of Mars. The dayside plasma envelope was found on first Mars orbiters (Vaisberg et al., 1976, Gringauz et al., 1976), but only the high temporal and mass resolutions of MAVEN instruments allowed investigations of the structure and processes of plasma of the dayside magnetosphere, the plasma layer which exists between shocked solar wind and ionosphere (Vaisberg et al., 2017). It was found that in the different dayside conditions the two different plasma layers form between the magnetosheath and ionosphere: (1) the mixture of heated ionospheric ions and energetic pick-up exospheric ions and (2) the layer of accelerated ionospheric ions population that forms the lower energy part of the plume formation. The first type of dayside magnetosphere of Mars is formed by the interaction of pick-up oxygen ions of exospheric origin with the topside of Mars' ionosphere (Vaisberg and Shuvalov, 2021). The second plasma layer between magnetosheath flow and ionosphere forms from initial lower energy part of the plume that is accelerated and continues in the magnetosheath. In this paper we show typical plasma populations, their properties and conditions that lead to formation of the dayside magnetosphere mainly from the material provided by the upper layer of the ionosphere. As the annex we include 115 dayside magnetosphere crossings of both types that were analyzed in the paper.