Sodium ion exosphere of Mercury during MESSENGER flybys

Abstract

Two flybys of Mercury by the NASA MESSENGER spacecraft on January 14 and October 6, 2008 provide insight into the spatial distribution of the heavy ion exosphere around the planet. The relatively quiet solar wind conditions and interplanetary magnetic field (IMF) orientation allow us to compare "in situ" observations with numerical simulations. During each flyby, the IMF had a strong radial Sun-Mercury direction but nonzero northward and southward components for the first (M1) and second (M2) flybys, respectively. We show that comparative studies of particle tracing in stationary electromagnetic fields from a self-consistent hybrid kinetic model provide a good characterization of Mercury's sodium ion exosphere when compared with MESSENGER observations. © 2010 by the American Geophysical Union.