Quasi-electrostatic fields in the near-earth space produced by lightning and generation of runaway electrons in ionosphere Original Research Article

Strong quasi-electrostatic fields (QESF) are generated in the ionosphere after positive lightning discharges by a succeeding redistribution of the induced spatial charges. These fields cause significant heating and modifications of both electron density and electric conductivity in the ionosphere. It is established that they also cause red sprites. According to recent observations, studying of initial period of QESF development is important for understanding sprite onset mechanisms. In the present paper QESF are modeled in these periods and the influence of different conditions on their structure is analyzed. First the structures of quasi-DC electric fields preceding a lightning discharge are investigated. The dependence of these structures on the magnetic field local orientation is taken into account by considering two latitudinal cases, corresponding to high and equatorial latitudes respectively. This is done analytically for each case. Then QESF are modeled which intensify with a beginning of a discharge between the cloud and the ground. Factors as conductivity profiles and the discharge time-scale are considered. Possibility of creation of runaway electron avalanches under QESF as a source of sprites, and their penetration into the magnetosphere, is evaluated.