Stimulated Ionospheric Scintillations and Absorption of Discreet Cosmic Sources Radiation Investigated with an Imaging HF Riometer

Abstract

The effects of enhanced dissipative absorption and increase of scintillation intensity for discreet cosmic sources (DCS) radiation in the polar ionosphere modified by the powerful HF heating have been considered. The investigations have been performed at 38 MHz with the use of the 64-beam riometer located at Alaska in immediate proximity to the HAARP heater. The results of two special heating campaigns of February and October 2008 when the artificially disturbed ionosphere domain was penetrated by the radiation from the two most powerful in the northern sky DCSs, namely Cassiopeia A and Cygnus A, have been discussed. The characteristic features of DCS scintillations induced by natural and artificial inhomogeneities of a Fresnel size in the F-layer of the polar ionosphere have been analyzed. The power spectra of the scintillations have been determined. They allowed recovering the characteristic parameters of the referred inhomogeneities and their motion velocity transverse to the source direction. The additional absorption of DCS radiation and the electron temperature increase in the D-region due to a powerful heater operation are estimated.