摘要：The surface impedance is defined to give the ratio between horizontal geoelectric and geomagnetic variation
fields at the earth’s surface in the frequency domain. Studying the properties of the surface impedance enables
conclusions about the corresponding relation between the surface electric and magnetic variation fields in the time
domain. In particular, it is possible to perform an investigation about assumptions that lead to a proportionality
between the geoelectric field and the time derivative of the geomagnetic field and about situations that make
the electric field and the variations of the magnetic field proportional. The results are directly applicable to the
research of geomagnetically induced currents (GIC) driven by the geoelectric field in technological networks at
the earth’s surface. Thus, the main objective of this paper is not in traditional magnetotellurics but in studies
of ground effects of space weather. We use a two-layer earth model, which is simple enough to have a precise
analytic formula for the surface impedance. It is shown in this paper that a poorly-conducting upper layer above
a highly-conducting bottom is favourable to the electric field (and GIC) being proportional to the magnetic time
derivative at the earth’s surface whereas a thin highly-conducting upper layer above a less-conducting bottom
results in a surface electric field (and GIC) proportional to magnetic variations.
关键词：Surface impedance ;geoelectric field ;geomagnetic field ;geomagnetically induced current ;GIC ;space weather ;plane wave ;layered earth
