Advancements in empirical geomagnetic field modeling during the Van Allen Probes era

Thursday, 18 December 2014
Grant K Stephens, Mikhail I. Sitnov, Haje Korth and Aleksandr Y Ukhorskiy, Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States
An empirical magnetic field model was developed with increased equatorial spatial resolution and fit to recent sources of inner-magnetospheric magnetometer data. The model describes the equatorial currents with a basis-function expansion approach, instead of custom-tailored current systems, allowing the equatorial currents to be inferred directly from data. This magnetometer data was binned using global storm parameters, allowing it to model the storm-time evolution of the magnetosphere during the March 2013 geomagnetic storm. It reconstructs the symmetric and asymmetric ring currents, including a westward ring current at R > 4 RE and a eastward ring current at R < 3 RE. The ring current is highly asymmetric during the main phase of the storm and returns to a symmetric ring current during the recovery phase. Other findings include a westward rotation and of the Region-2 ring current system during the main phase of the storm and a closed banana current in the inner-magenteosphere closing through asymmetries in the westward and eastward ring current system, both of which are consistent with first-principles kinetic models.