Two Plasma Sources of Dayside Martian Magnetosphere: Pick-up Ions -- Ionosphere Interaction

TL;DR

This study uses MAVEN data to analyze the structure and plasma populations of the dayside Martian magnetosphere, revealing the presence of heated ionospheric ions and heavy pick-up ions originating from the magnetosheath.

Contribution

It provides new insights into the composition and dynamics of the dayside magnetosphere of Mars, especially the role of magnetosheath-origin heavy ions.

Findings

Heated ionospheric ions are present in the magnetosphere boundary layer.

Heavy pick-up ions originate from the magnetosheath and influence magnetosphere formation.

Magnetosheath ions are key energy sources for the upper ionosphere.

Abstract

Dayside magnetosphere of Mars is a thin layer with usually increased magnetic field and heated planetary ions between the magnetosheath and the ionosphere. The Mars Atmosphere and Volatile Evolution Mission (MAVEN) spacecraft provided, for the first time, high temporal and spatial resolution measurements enabling to study the structure of this region. The region was given several names including the boundary layer, the plasma mantle, and magnetosphere. The outer boundary of this region was called magnetopause, ionopause, ion composition boundary and pile-up boundary (see Espley, 2018). We analyze the properties and plasma populations in the layer between the magnetosheath flow and ionosphere on the day side of Mars. The region with the Solar-Zenith Angle (SZA) between 40{\deg} and the subsolar point is considered. It was found that the region between magnetopause and ionosphere filled with the heated diluted ionospheric ions and the heavy pick-up ions is formed in magnetosheath. So, it is found that this region of heated ionospheric ion is collocated with another heavy ions component which has magnetosheath origin. This magnetosheath component was eluded from identification due to two reasons. First one is that the second component looked like the high-energy tail of the heated ionospheric component on energy-time spectrograms. Second one is that STATIC energy-mass analyzer's energy range was shortened in the ionosphere diminishing observations of the higher energy ions. It appears that the magnetosheath ion component is important factor of formation of dayside magnetosphere and the source of energy in upper ionosphere and atmosphere.