Can seismogenic atmospheric current influence the ionosphere?

Abstract

The question of whether earthquake precursors can arise in the ionosphere is of a special interest in geophysics. Despite numerous encouraging reports on seismo-ionospheric effects, the mechanism of the lithosphere-atmosphere-ionosphere coupling (LAIC) during the crust destruction phase was not revealed yet. One of hypothesis assumes that a seismogenic current transfers an abnormal electric field from the near-surface atmosphere to the ionosphere prior to an earthquake occurrence. This current can be caused by the air ionization due to enhancement of radon gas emission from the soil or upward movement of charged atmospheric aerosols. Here we present a theoretical model of the spatial structure of the electric field in the atmosphere and bottom ionosphere driven by a vertical external current in the lower atmosphere. Perturbation of electric field in the ionosphere has been derived in the approximation of the "thin" E-layer. Simple analytical estimates have been obtained that relate the horizontal electric field in the ionosphere, vertical electric field on the ground, and parameters of the external current. The electric field attenuation with altitude is caused by the increase of atmospheric conductivity and the horizontal spreading of current. The estimates obtained enable one to evaluate the feasibility of anomalous variations of electric fields in the ionosphere related to forthcoming earthquakes. The analysis has shown that the hypothesis on aerosol upward convection as a cause of ionospheric anomalies seems unrealistic. To interpret the occurrence of significant ionospheric anomalies it would be necessary to assume the presence of too large currents and electric fields in the lower atmosphere that had never been observed during non-thunderstorm periods.