Abstract
We have compiled a global three-dimensional (3D) conductivity model of the Earth with an ultimate goal to be used for realistic simulation of geomagnetically induced currents (GIC), posing a potential threat to man-made electric systems. Bearing in mind the intrinsic frequency range of the most intense disturbances (magnetospheric substorms) with typical periods ranging from a few minutes to a few hours, the compiled 3D model represents the structure in depth range of 0–100 km, including seawater, sediments, earth crust, and partly the lithosphere/asthenosphere. More explicitly, the model consists of a series of spherical layers, whose vertical and lateral boundaries are established based on available data. To compile a model, global maps of bathymetry, sediment thickness, and upper and lower crust thicknesses as well as lithosphere thickness are utilized. All maps are re-interpolated on a common grid of 0.25×0.25 degree lateral spacing. Once the geometry of different structures is specified, each element of the structure is assigned either a certain conductivity value or conductivity versus depth distribution, according to available laboratory data and conversion laws. A numerical formalism developed for compilation of the model, allows for its further refinement by incorporation of regional 3D conductivity distributions inferred from the real electromagnetic data. So far we included into our model four regional conductivity models, available from recent publications, namely, surface conductance model of Russia, and 3D conductivity models of Fennoscandia, Australia, and northwest of the United States.
Highlights
Strong eruptions at the Sun’s surface produce a large release of matter, which, with a speed reaching 800–1000 km/s, flows into interplanetary space
If the Earth appears to be on the way of the solar wind, its interaction with the Earth’s magnetosphere and the ionosphere leads to an abnormal disturbance of a fluctuating geomagnetic field
We briefly discuss the main features of the global conductivity distribution that can be recognized from the model
Summary
Strong eruptions at the Sun’s surface produce a large release of matter (plasma), which, with a speed reaching 800–1000 km/s (the solar wind), flows into interplanetary space. If the Earth appears to be on the way of the solar wind, its interaction with the Earth’s magnetosphere and the ionosphere leads to an abnormal disturbance of a fluctuating geomagnetic field. Alekseev et al Earth, Planets and Space (2015) 67:108 current system from the horizontal magnetic field, the estimated amplitude of this current system may vary from 1 to 2, depending on actual conductivity distribution in the Earth. 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)
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