The Influence of Solar Wind Pressure on Martian Crustal Magnetic Field Topology

Abstract

We present a study of changes in Martian magnetic topology induced by upstream solar wind ram pressure variations. Using electron energy spectra and pitch angle distributions measured by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we classify the topology of magnetic field lines in the Martian space environment across a range of solar wind conditions. We find that during periods of high solar wind dynamic pressure, draped fields are pushed to lower altitudes on the dayside of the planet, compressing closed fields. At the same time, open topology becomes more prevalent on the nightside due to the broadening of crustal cusp regions. The result is a decrease in closed topology at all locations around Mars, suggesting that the Martian ionosphere becomes significantly more exposed to solar wind energy input during high solar wind pressure. This could likely contribute to elevated levels of ion escape during these periods.