# The Effects of Solar Wind Dynamic Pressure on the Structure of the Topside Ionosphere of Mars

## TL;DR

This study investigates how variations in solar wind dynamic pressure influence the structure of Mars's topside ionosphere, revealing plasma depletion, magnetic field changes, and implications for ion escape and plasma transport.

## Contribution

It provides new insights into the impact of solar wind dynamic pressure on Mars's ionosphere using combined observational data, highlighting plasma depletion and magnetic field responses.

## Key findings

- High solar wind pressure causes plasma depletion in the topside ionosphere.
- Increased magnetic field strength correlates with plasma depletion.
- High solar wind pressure leads to ionospheric compression and enhanced ion escape.

## Abstract

We use Mars Atmosphere and Volatile EvolutioN observations of the upstream solar wind, and Mars Express observations of ionospheric electron densities and magnetic fields, to study how the topside ionosphere ($>$ 320 km) of Mars is affected by variations in solar wind dynamic pressure. We find that high solar wind dynamic pressures result in the topside ionosphere being depleted of plasma at all solar zenith angles, coincident with increased induced magnetic field strengths. The depletion of topside plasma in response to high solar wind dynamic pressures is observed in both weak and strong crustal magnetic field regions. Taken together, our results suggest that high solar wind dynamic pressures lead to ionospheric compression, increased ion escape, and reduced day-to-night plasma transport in the high-altitude nightside ionosphere.