Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

With this technique, the observations do not depend on sunlight, may be conducted trough a moderately thick higher cloud cover, and are not significantly affected by aerosols. Retrieval of ozone vertical profiles was performed by the model-fitting method as described by de la Noe et al [3]. As retrieval procedure, model vertical distribution of pressure and temperature [4] were used. Uncertainty o f retrieval depends on radio measurement errors and systematic artifacts of the ozone spectrum and generally is about 20 % at altitude region from 20 km up to 60 km. During the heating experiments the ozonemeter operated at all times from March 14 till March 19. Such twenty- four-hour observations allowed finding also the diurnal variation of the ozone number density in the mesosphere at altitudes of ~ 60 km, which are a result of sunrise/sunset phenomena. Experimental results Heating o f the ionospheric D-region was conducted on March 14 from 11:30 till 15:00 LT, on March 15 from 12:11 till 14:41 LT, on March 16 from 12:01 till 14:31 LT, and on March 17 from 11:40 till 13:10 LT. During these seances the Sura facility was operated on [30 min - on, 30 min - off] scheme. It allowed to obtain in twos ozone line spectra during both heater -on and -o ff periods. It should be mentioned that all experiments were conducted under quite geomagnetic conditions. Fig. 2 displays the spectral data from microwave measurements made on March 14. In the left-hand panel of the figure it is shown spectra of ozone emission intensities registered when the atmosphere was HF-pumped (black line) and when the PW was switch-off (gray line). In the right-hand panel it is shown spectra o f the ozone emission intensities registered under night (black line) and day (gray line) conditions. To produce these spectra high frequency and low frequency wings o f the measured ozone line were overlaid and averaged in order to reduce the random noise component. Data represented in the left hand panel clearly demonstrate that the HF pumping o f the atmosphere tends to decrease measured emission intensities at frequency offsets |Af| < 40 MHz relatively to the line center. We have to emphasize that the value of such decreasing is comparable with the diurnal variation of ozone emission intensity. Influence o fHFpowerful waves on the ozone content in the Earth's atmosphere Frequency, MHz Frequency, MHz Fig. 2. Changes in ozone line spectral characteristics by HF pumping of the atmosphere (left panel) and the diurnal variation of the ozone line emission intensities (right panel). March 14, 2009. 175