Peculiarities of artificial ionospheric radiation under the action of high-power HF radiowaves, emitted by the SPEAR facility, on the sporadic E layer of the polar ionosphere

摘要

The results of the experimental studies of the ionospheric effects originating under the action of high-power HF radiowaves, emitted by the SPEAR heating facility into the sporadic E (s) layer of the polar ionosphere, are presented. The experiment was performed on March 2, 2007, simultaneously at two spaced points: Barentsburg (Spitsbergen, a distance of about 40 km from the SPEAR facility) and Gor'kovskaya observatory near St. Petersburg, located at a distance of about 2000 km from SPEAR. The distributions of the heating signal intensity in the 100 kHz frequency band were measured in Barentsburg. Bistatic backscatter of diagnostic HF signals by small-scale artificial ionospheric irregularities was observed at Gor'kovskaya observatory. Based on an analysis of the experimental data obtained in Barentsburg, it has been found out that a broadband noise-like component originated and additional maximums appeared in the heating signal spectrum. The broadband emission intensity was a factor of 1.5-3 as high as the noise level. The additional maximums were formed in the regions of the positive and negative frequency shift relative to the heating signal frequency and were observed when the heating frequency was lower than the critical frequency of the E (s) layer; e.g., a high-power HF radiowave reflected from E (s) . The expression for determining the frequency shift of the additional maximum in the heating signal spectrum at altitudes of the ionospheric E region, taking into account the ion-electron collision frequency, has been obtained. The heating signal spectrum registration was compared with the observations of small-scale artificial ionospheric irregularities and the trajectory modeling of signals scattered by the considered irregularities. The observation results have been analyzed and interpreted taking into account the magnetic and ionospheric data characterizing the background geophysical conditions.