Abstract

First, the HF pumping of the ionospheric F-region at the frequencies 4.5--7 MHz causes the enhancement of the electromagnetic emission from the pumped volume of the ionosphere at the frequencies f~600 MHz by 0.3$--1.3 K. The emission is excited at the altitudes 195--220 km above the Sura facility. The characteristic times of the UHF SEE development and decay were found to be of order of few tens of seconds. The emission is tentatively attributed to an excitation of high Rydberg states of the neutral particles by the accelerated electrons, but this requires further experimental and theoretical study.

Second, the results of correlated study of the pump induced optical emission in the green line of atomic oxygen (conditioned by accelerated electrons) and the HF SEE are presented for special diagnostic schedule of the pumping are presented. It our experiments the airglow was observed just after transition of the pump wave from the continuous radiation to short pulse radiation. This corresponds to the initial stage of the decay of so-called striations, which is confirmed by HF SEE measurements.

Third, accelerated electrons cause an additional ionization of the ionospheric plasma. The additional ionization is studied by multifrequency Doppler sounding of the ionosphere modified volume. In our experiments, a dependence of the additional ionization efficiency on the relation between the pump frequency and harmonics of the electron cyclotron frequency was investigated for the 4th, 5th and 6th harmonics.

The work is supported by RFBR grant no. 03-02-16309.

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