Comparing Three Approaches to the Inducing Source Setting for the Ground Electromagnetic Field Modeling due to Space Weather Events

Abstract

Ground‐based technological systems, such as power grids, can be affected by geomagnetically induced currents (GIC) during geomagnetic storms and magnetospheric substorms. This motivates the necessity to numerically simulate and, ultimately, forecast GIC. The prerequisite for the GIC modeling in the region of interest is the simulation of the ground geoelectric field (GEF) in the same region. The modeling of the GEF in its turn requires spatiotemporal specification of the source which generates the GEF, as well as an adequate regional model of the Earth’s electrical conductivity. In this paper, we compare results of the GEF (and ground magnetic field) simulations using three different source models. Two models represent the source as a laterally varying sheet current flowing above the Earth. The first model is constructed using the results of a physics‐based 3‐D magnetohydrodynamic (MHD) simulation of near‐Earth space, the second one uses ground‐based magnetometers’ data and the Spherical Elementary Current Systems (SECS) method. The third model is based on a “plane wave” approximation which assumes that the source is locally laterally uniform. Fennoscandia is chosen as a study region and the simulations are performed for the September 7–8, 2017 geomagnetic storm. We conclude that ground magnetic field perturbations are reproduced more accurately using the source constructed via the SECS method compared to the source obtained on the basis of MHD simulation outputs. We also show that the difference between the GEF modeled using laterally nonuniform source and plane wave approximation is substantial in Fennoscandia.

Real‐Time 3‐D Modeling of the Ground Electric Field Due To Space Weather Events. A Concept and Its Validation

“…We took the 3-D conductivity model of the region from Marshalko et al (2021), where it was constructed using the SMAP (Korja et al, 2002)-a set of maps of crustal conductances (vertically integrated electrical conductivities) of the Fennoscandian Shield, surrounding seas, and continental areas. The SMAP consists of six layers of laterally variable conductance.…”

“…To justify the value for T we first calculate the reference ("true") time-domain electric field for the chosen 8-hr event. This reference field was computed using the procedure presented in Ivannikova et al (2018) and Marshalko et al (2020Marshalko et al ( , 2021. Specifically, we calculate j ext (t, r) using Equations 13 and 15 and taking 21 terms in Equation 13.…”

“…Specifically, we calculate j ext (t, r) using Equations 13 and 15 and taking 21 terms in Equation 13. Further, according to Marshalko et al (2021), we calculate the reference electric field as follows:…”

“…Third, the regional magnetometer network (International Monitor for Auroral Geomagnetic Effect (IMAGE; Tanskanen, 2009)), allows us to build a realistic model of the source. Finally, the last but not the least consideration to choose this region is the fact that we have already performed a comprehensive 3-D EM model study in this region (Marshalko et al, 2021).…”

“…This set up, in particular, means that S was computed at M = 72 × 48 = 3,456 grid points and N = 2,880 time instants. Note that the same event, region and grid were considered in our recent study (Marshalko et al, 2021). The PCA of S m (t) is performed in a similar manner as it was done, for example, in Alken et al (2017), Egbert et al (2021), andZenhausern et al (2021).…”