Examining Three Approaches to the Construction of an Inducing Source for the Ground Electric Field Modeling during Space Weather Events

Abstract:

Ground-based technological systems can be significantly affected by geomagnetically induced currents (GIC) during space weather events. Knowing the geoelectric field (GEF) and the geometry and parameters of a technological network in the region of interest, it is possible to estimate GIC in the network. To model the GEF, it is necessary to know the spatiotemporal distribution of inducing currents (the source) as well as the distribution of the Earth's electrical conductivity. In this work, we compare GEFs induced by three different models of the source in a 3-D conductivity model of Fennoscandia during the 7-8 September 2017 geomagnetic storm. The two source models are laterally varying sheet currents. The first model is constructed on the base of a 3-D magnetohydrodynamic (MHD) simulation of near-Earth space, whereas the second one is based on the use of ground magnetometers' data and the Spherical Elementary Current Systems (SECS) method. In the third approach the GEF is calculated using plane wave excitation (so-called impedance method).

We conclude that magnitudes of magnetic field perturbations in Fennoscandia are underestimated, when "MHD" source is exploited. Subsequently, the magnitudes of the GEF simulated using this source are few times lower than those obtained via modeling with the "SECS" source. Another result of the study is that in Fennoscandia the GEF modeled with the use of the "MHD" or "SECS" sources differ much from the GEF modeled using plane-wave excitation.