Cosmic Ray Cutoff Predictions Using Magnetic Fields From Global Magnetosphere MHD Simulations

The cutoff rigidity of relativistic particles (cosmic rays, solar energetic particles, etc.) that enter the magnetosphere and atmosphere have traditionally been determined with numerical particle orbit integration calculated backwards in time utilizing a suitable magnetic field model. Such models were usually of empirical nature, such as the IGRF and Tsyganenko models. At mid-latitudes and near the polar cap boundary, however, such magnetic field models may not be very accurate during geomagnetic storm times. In this study we therefore employ a magnetospheric magnetic field from a global MHD simulation of the Earth's magnetosphere. We compare our results with those from simpler models, like IGRF and Tsyganenko 1996, for quiet times as well as for magnetically disturbed times.