Artificial ionospheric cavity induced by the radiation from the “sura” facility

On October 24, 1997, from 16:00 to 19:30 LT, during experiments on the artificial mofification of ionosphere by powerful HF radiation using spaced heating, we recorded twice a significant (tens of percent) decrease of the electron number density in the F-layer, synchronous with the operation of the heating trnasmitters. The critical frequency of this layer decreased by 10–20%. This points to the possibility of artificial generation of large-scale inhomogeneities of the ionospheric plasma density using spatially split heating. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 7, pp. 682–690, January 1999.