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.

10 years investigations o fthe solar UV radiation and total ozone in Stara Zagora, Bulgaria is achieved, which with this multiwave method is 5% [ 6 ]. GOME is a spectrometer, measuring the spectrum of the Earth’s light flux - mainly solar, which is reflected by the atmosphere back to space as well as the direct solar spectrum. The relation between the intensity of the flux, reflected by the Earth and the direct solar signal is used to calculate the total ozone content. The instrument measures the spectra in a wide range - from 240 nm to 790 nm with high resolution (0.2 - 0.4 nm) TOMS-ЕР continues the NASA Program for mapping and research of the global ozone distribution in the Earth’s atmosphere since 1996. The TOMS measurements cover the near ultraviolet region o f the electromagnetic spectrum where the solar radiation is partially absorbed by the ozone. The intensity is registered in 6 wavelengths. TOMS measures the total ozone content in an atmospheric column from the Earth’s surface to the upper atmospheric boundary under any geophysical daily conditions. SCIAMACHY is an imaging spectrometer, which carry out global measurement of various trace gases in the troposphere and stratosphere. They are retrieved from the instrument by observation of transmitted, back scattered and reflected radiation from the atmosphere in the wavelength range between 240 nm and 2400 nm. In Nadir Mode, the global distribution (total column values) of the atmospheric trace gases, including ozone, is observed. Major results From the measurements made using the scanning spectrophotometer Photon a number of direct solar spectra was obtained. This allows the investigation of UV solar radiation reaching the Earth’s surface at different conditions. Because a clear sky is necessary for direct solar spectra, there isn’t frequent such measurements during the winter-spring period. Typical Photon’s spectra are shown in Fig. 1. Wavelength, nm Fig. 1. UV solar spectra, registered by Photon , at different solar zenith angle: (1) SZA=53, (2) SZA =22. The dependence analysis o f the UV radiation on the solar zenith angle (SZA) at fixed total ozone shows a decrease of all wavelengths intensities with the increase of the SZA, but different for each of them. 140 Solar Zenith Angle, degrees Fig. 2. Dependence o f the UV irradiance on the solar zenith angle atfixed TOC. Total ozone, DU Fig. 3. Dependence o f the 305 nm wavelength irradiance on the TOC, using Photon data. The shorter wavelengths change more than the longer ones with equal changes of SZA. The results, presented in Fig. 2, show that the radiation at used wavelengths changes approximately with an order of 2 in (26° - 72°) SZA interval. Fig. 3 shows instantaneous values of solar UV irradiance at 305 nm measured at 30° SZA together with the total ozone. Reduction in the ozone leads to an increase of these wavelengths reaching the Earth’s surface. The inverse relationship of these two variables is significant (r = -0.62 ± 0.18) at 98% confidence level. The dynamics of the total ozone content over Stara Zagora is investigated using data from TOC measurements by the ground-based spectrophotometer Photon as well as by satellite instruments. Fig. 4 shows the annual TOC variations by data of Photon and GOME (Fig. 4a) and by Photon and TOMS-ЕР (Fig. 4b). A good agreement between the ground-based and the satellite data, as well as seasonal variations can be seen. These variations are expressed by an abrupt maximum in the spring and a gently sloping decrease in the autumn. The difference between the maximum and 179