ALBERT

Description: We will present results from an interdisciplinary project to combine ground-based and satellite data, physics-based modeling with the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM), and three dimensional (3D) modeling of induced geo-electric fields to map ionospheric current systems and Geomagnetically Induced Currents (GICs). Our approach builds on our previous efforts to develop an empirical model of diurnal variation magnetic fields, with the goal of imaging deep Earth electrical conductivity (Egbert et al., 2021, GJI; Zhang et al., 2022, Science Advances). We use frequency domain principal components analysis (PCA) of ground-based data to decompose magnetometer array data as a sum over a modest number of temporal/spatial mode products. Fully 3D spatial structure of current systems associated with each temporal mode are then derived by fitting both ground-based and satellite magnetometer data, using basis functions for 3D ionospheric source currents derived from PCA of TIEGCM outputs. In combination, the temporal and spatial modes yield data and physics constrained models of storm-time magnetic fields, which we are using to force 3D electromagnetic induction models, and to study electric fields induced in a realistic Earth conductivity model, by realistic storm-time source fields. Initial results have been obtained for two storms, and these are now being analyzed to study interactions between storm spatial structures and 3D Earth conductivity. Our study will allow us to assess whether standard approaches based on local uniform-source magnetotelluric impedances are adequate, and to nunderstand better optimal spacing of ground observations needed for situational awareness.