Annual variations in the electromagnetic field of the earth and electrical conductivity of the geological environment

Synchronous annual variations in the geoelectric and geomagnetic field are studied on the basis of long-term electromagnetic monitoring. It is shown that the annual geoelectric variations have intraterrestrial origin and are not related to the annual geomagnetic variations. Temporal variations in the magnetotelluric impedance and magnetic tipper, which characterize the electrical conductivity of the geological environment, are analyzed. It is established that annual variations in the magnetotelluric impedance mainly describe the variations in the electrical conductivity of surface crustal layers and are less sensitive to the deep electrical conductivity of the Earth. The annual variations in the imaginary magnetic tipper at the periods of 1000–3000 s probably reflect the changes in conductivity of a deep transversal low-resistive zone (the fault). It is suggested that annual variations in the geoelectrical and geomagnetic fields, as well as in the electrical conductivity of the geological environment, arise as a response to the changes in the geodynamical processes caused by the revolution of the Earth around the Sun.