Effects of Earth Resistivity and Coast Dip Angle on Coastal Effect during Geomagnetic Storms

In order to explore the influence of earth resistivity and coast dip angle on coastal effect in geomagnetic storm process, this paper selects the typical New Scotia area as the research object, the corresponding earth resistivity model is established by using the finite element method. The induced electric field on the earth surface is calculated by changing coast dip angle and the surface and subsurface earth resistivity. From the results, when the resistivity of surface layer is almost the same as that of sea water, the coastal effect is not obvious, and with the increase of coast dip angle, the surface electric field in offshore area increases slightly. When the surface resistivity is larger than the seawater resistivity to a certain extent, the coastal effect will make the surface electric field in the offshore area larger than that in area away from coast, and the smaller the coast dip angle is, the more obvious this trend is. The surface induced electric field in area away from coast will not be affected by the coastal effect, so it will not be affected by the coast dip angle. The influence of subsurface resistivity on the surface electric field in both offshore area and area away from coast is the same: with the increase of subsurface resistivity, the surface induced electric field gradually decreases and finally tends to be stable. When the surface resistivity is determined, the influence of the coast dip angle on the surface electric field is small. The results of this paper can provide reference for coastal effect calculation and GIC hazard assessment during geomagnetic storms.