Lower ionosphere large-scale disturbances caused by powerful non-stationary radiation

Abstract

The relevance of this study is due to the need of studying largescale (~ 560 km) disturbances in the lower ionosphere, which can be due to coupling among the subsystems in the Earthatmosphere-ionosphere-magnetosphere system. Until recently, the effects arising within the antenna beam have mainly been studied. The Sura heater near Nizhny Novgorod was used to stimulate disturbances in the ionospheric plasma, and the ionosonde near Moscow city was used as a diagnostic facility. The heater turn on/off resulted in an increase of 1.2 to 1.6 MHz in the minimum observable frequency in the ionograms during the night and day times, respectively. This frequency increase is caused by an increase in absorption of sounding radio waves due to an increase in the lower ionosphere electron density. The latter is probably due to energetic (~ 100 keV) electron precipitation from the magnetosphere into the lower ionosphere. Electron flux estimates are of the order of 107÷108 m−2⋅s−1. The accumulation, switching off/on, and impact effects have been proved to exist.