Estimation of a Tropospheric Electric Field Associated with the African Zone of Thunderstorm Activity that Penetrates the Ionosphere

The penetration of the nighttime ionosphere by electric fields in the African zone of thunderstorm activity is studied based on calculations. These fields are caused by both the Coulomb charges of thunderclouds and the electric current generated by them as elements of the global electric circuit in the studied zone. An electric field is produced by the sum of Coulomb fields from each of the 600 thunderclouds in the zone in the first case and by an average total upward current of 600 A in the second case (1 A from each thundercloud, when it is considered an elementary, bipolar, point, quasi-stationary current source within the global atmospheric electrical circuit model in the African zone of thunderstorm activity). It is found that tropospheric Coulomb charges produce weak electric fields (of no more 1 μV/m) in the ionosphere. However, an ionospheric electric field produced by the total current from thunderclouds in the African zone of thunderstorm activity can attain ~0.2 mV/m at ionospheric altitudes at night in winter during periods of low solar activity.