The Evolution of the Inner Magnetosphere during CME- and CIR-Driven Geomagnetic Storms

Abstract:

We investigated the access of ions of ionospheric and solar wind origin to the near-Earth magnetotail and inner magnetosphere during geomagnetic storms caused by the impact of a coronal mass ejection (CME) and by corotating interaction regions (CIRs) and high-speed streams, and the acceleration these ions undergo during their transport. We carried out a large-scale kinetic simulation of the magnetosphere for each of the storms examined, using time-dependent global electric and magnetic fields obtained from a global magnetohydrodynamic simulation of each storm events. Oxygen ions were launched from the ionosphere, and protons from the solar wind for several hours prior to storm onset and well into the recovery phase of each storm.

For each storm, we delineate the response of the MHD simulation to solar wind driving, the geoeffective access of solar wind and ionospheric ions to the inner magnetosphere, and the characteristics of these ions, including density, pressure, temperature, and temperature anisotropy. We also delineate the physical processes responsible for ion acceleration during each storm event by examining the evolution of entropy for each ion species during each storm.