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.
Highlights
Eruptions at Sun’s surface blow large quantities of charged particles into space
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
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
Summary
Eruptions at Sun’s surface (coronal mass ejections) blow large quantities of charged particles into space. The particle streams interact with Earth’s magnetic field, intensifying the westward directed magnetospheric ring current (Love, 2008). This phenomenon, leading to substantial temporal variations of the geomagnetic field, is known as geomagnetic storm. According to Faraday’s law of induction, the fluctuating geomagnetic field in turn generates an electric field and induces currents in Earth and grounded conducting networks, such as power grids and pipelines (Pirjola, 2000) These geomagnetically induced currents (GIC) can lead to severe damages of the power network, as happened, for example, 1989 in Quebec (Kappenman et al, 1997). Understanding the properties of the geoelectric field is a key consideration in estimating the hazard to technological systems from space weather (Pulkkinen et al, 2007)
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