Towards quantitative assessment of the hazard from space weather. Global 3-D modellings of the electric field induced by a realistic geomagnetic storm

Abstract

In order to estimate the hazard to technological systems due to geomagnetically induced currents (GIC), it is crucial to understand the response of the geoelectric field to a geomagnetic disturbance and to provide quantitative estimates of this field. Most previous studies on GIC and the geoelectric field generated during a geomagnetic storm assume a 1-D conductivity structure of Earth. This assumption however is invalid in coastal regions, where the lateral conductivity contrast is large. In this paper, we investigate the global spatio-temporal pattern of the surface geoelectric field induced by a typical major geomagnetic storm in a conductivity model of Earth with realistic laterally-heterogeneous oceans and continents. Exploiting this model makes the problem fully 3-D. Data from worldwide distributed magnetic observatories are used to construct a realistic model of the magnetospheric source. The results of our numerical studies show large amplification of the geoelectric field in many coastal regions. Peak amplitudes obtained with 3-D modelling exceed the amplitudes obtained in a 1-D model by at least a factor 2, even if the latter makes use of the local vertical conductivity structure. Lithosphere resistivity is a critical parameter, which governs both amplitude and penetration width of the anomalous electric field inland.

Influence of spatial variations of the geoelectric field on geomagnetically induced currents

“…The geoelectric field varies rapidly temporarily and spatially as demonstrated, for example, by Beggan et al (2013), Bedrosian and Love (2015), Wei et al (2013) and Wang et al (2016) for regional and continental scales, and by Püthe and Kuvshinov (2013) and Ngwira et al (2015) for global scales. Temporal variations are due to time variations of space currents and are connected with time variations of the geomagnetic field by Faraday's law.…”

Reproducing electric field observations during magnetic storms by means of rigorous 3-D modelling and distortion matrix co-estimation

“…The methodology of Püthe and Kuvshinov (2013) is self-consistent, but depending on location, the presented results might still over-or underestimate the amplitudes of the actual electric field. This is due to galvanic effects, i.e.…”

“…A technique to model the geoelectric field induced by large-scale magnetospheric currents in a 3-D conductivity model of the Earth was presented by Püthe and Kuvshinov (2013), based on a previous study by Olsen and Kuvshinov (2004). The authors used precomputed electromagnetic (EM) responses of the 3-D model and magnetic data from the global network of geomagnetic observatories to construct the magnetospheric source, described by spherical harmonic expansion (SHE) coefficients.…”

Compilation of 3D global conductivity model of the Earth for space weather applications

“…Püthe and Kuvshinov 2013). This model has been shown to be adequate to reproduce large-scale geomagnetic storm electric fields (Püthe et al 2014), but it is most probably not sufficient for accurate characterization of smaller-scale magnetospheric substorm electric fields due to higher frequency content of their spectrum.…”

“…Because the conductivity can vary several orders of magnitude, this affects strongly the electric field. In case of a true 3D Earth, a more complex behavior of magnetic and electric fields may occur locally, especially in the regions with highconducting near-surface anomalies (Beggan et al 2013;Pulkkinen and Engels 2005;Püthe and Kuvshinov 2013;Thomson et al 2005;Viljanen et al 2014;Wei et al 2013). …”