Modeling of Oxygen ions in inner magnetosphere during substorms

The HENA instrument on IMAGE has observed significant increases in the Oxygen energetic neutral atom (ENA) signature during substorm events. The Hydrogen signature for the same events show relatively small change. We use a particle trajectory simulation developed by Delcourt to simulate the response of magnetospheric Oxygen ions to dipolarization of the geomagnetic field. Our results show strong injection in the pre-midnight sector during the expansion phase consistant with observed events.