Main ionospheric trough studied from intercosmos-Bulgaria-1300

Abstract The main ionospheric trough is a phenomenon in the mid and high latitude ionosphere, characterized by an abrupt decrease of the electron and ion density and increase of the electron temperature. We here examine the behaviour of the trough for different geomagnetic conditions based on data from the Intercosmos-Bulgaria-1300 satellite. The dependence of the polar trough wall on the boundary of the soft electron precipitation from the plasma layer is shown, and a possible universal time dependence is examined.