Messenger observations of mercury s northern cusp have indicated that many questions remain concerning processes of solar wind entry, precipitation onto the surface and generation of planetary ions.…

This is a $457,294 grant awarded by the National Aeronautics and Space Administration (NASA) to the Regents of the University of Michigan to conduct research on the processes of solar wind entry, precipitation onto the surface, and generation of planetary ions in Mercury's northern cusp. The research objectives include studying the geometry of magnetopause reconnection, analyzing the behavior of three planetary ion species in the cusp, and analyzing the precipitating flux in proton observations through the cusp. The research will utilize data from the MESSENGER spacecraft as well as advanced multi-scale modeling techniques. This grant does not have a set-aside designation.

Messenger observations of mercury s northern cusp have indicated that many questions remain concerning processes of solar wind entry, precipitation onto the surface and generation of planetary ions. We propose to address these questions with a detailed, multi-faceted investigation, based on analyses of plasma observations and facilitating their interpretation with modeling. Our first objective is to study the geometry of magnetopause reconnection through messenger observations in cusp. We will characterize energy dispersion signatures observed there and use them to determine the location of their parent reconnection events. Our second objective is to analyze the observed behavior of three planetary ION species in the cusp, especially relating to their sources and sinks. We will then use coupled kinetic MHD modeling to tie observations to physical processes, testing several hypotheses concerning the sources and sinks of these ions in the cusp, e.g. that heavy neutrals ionized near the subsolar magnetopause are swept back into the cusp at energies of>1 KEV while 100-300 EV ions are accelerated locally in the cusp. Our third objective is to analyze the precipitating flux in proton observations through the cusp. We will combine these data with MHD-estimated cusp areas to calculate the total precipitation rate in the cusp. The proposed work will be based solidly on analysis of data from the messenger fips and MAG instruments, as already established in published work. For the first time at mercury, we will employ the adaptive mesh particle simulator (amps) kinetic model [tenishev ET AL., 2013] fully coupled to a state-of-the-art MHD magnetosphere model (batsrus), on a per time step basis. These coupled models can capture single particle dynamics for heavy ions while accurately representing the evolving state of the global magnetosphere. This unique multi-scale modeling is key to understanding the highly dynamic and potentially non-adiabatic behavior observed in heavy ions in mercury s cusps. This study will substantially enhance our understanding of solar wind and planetary ION processes in mercury s cusps and their implications for mercury s surface, neutral exosphere and magnetosphere.