Penetration of an electrostatic field from the lithosphere into the ionosphere and its effect on the D-region before earthquakes

The penetration of an electrostatic field, from a source located in the lithosphere into the ionosphere is investigated. The electrostatic problem is solved numerically for a medium with an inhomogeneous anisotropic conductivity coupled to an "effective upper boundary condition". The results show that the electric field in the ionosphere D-layer can effectively change the parameters of the lower ionosphere. The kinetics in the D-region are considered along with calculations of the atmospheric conductivity at an altitude of 60 km. It is concluded that (i) the atmospheric conductivity at 60 km can change by 30-70% as a result of electrostatic perturbations, created before the onset of earthquakes, and (ii) the penetration of an electrostatic field from th e lithosphere into the ionosphere above 60 km is much better at night-time than during the day. (C) 2003 Elsevier Science Ltd. All rights reserved.