Surface electric fields for North America during historical and extreme geomagnetic storms

We are developing surface electric field scenarios for the continental U.S. to better understand the impact of geomagnetic disturbances (GMDs) on the electric grid. These surface electric field time-series are created for both historical (1980-2009) and simulated extreme geomagnetic storms (up to 1-in-100 year storms). Using the spherical elementary current system method (SECS), we interpolate the sparsely distributed magnetometer data across North America. This interpolated magnetic field data is combined with surface impedances from the United States Geological Survey for physiographic regions to create a database of horizontal, orthogonal surface electric field maps in one-minute time steps during each storm. We consider the average and peak electric field amplitudes, typical durations of elevated electric field fluctuations, as well as regions most severely affected by geomagnetic storms. The induced surface electric field strongly depends on the local surface impedance – we discuss the relative response of different physiographic regions to different sets of magnetic field inputs.