Global Simulations of Mercury's Quasi-Trapped Particle Population

The radiation belts are well known in the Earth's inner magnetosphere where solar wind particles are trapped forming a toroidal region with relativistic energy particles. Because Mercury's magnetic moment is about 10000 times weaker than Earth's, a long-standing question is whether Mercury has such a radiation belt since the magnetosphere is much smaller and the day-side magnetopause is compressed significantly towards the planet surface. Global hybrid simulations of Mercury's magnetosphere indicate a region of trapped particles does exist around the planet with relatively low energies (~ keV). I n March 2011, the MESSENGER spacecraft entered into orbit around Mercury, providing measurements that can confirm these simulation findings. We will present simulation results, focusing on the inner magnetosphere of Mercury together with a comparison of in-situ measurements from the MESSENGER spacecraft in order to understand the properties of the quasi-trapped particle population.