Alexander V. Mikhalev

The manifestation of seismic activity in 557.7 nm emission variations of the earth's upper atmosphere

Abstract For the Baikal seismic zone (East Siberia region, 52°N, 103°E) the Earths upper atmosphere radiation parameters were analysed for 557.7 nm emission line of atomic oxygen [OI] (de-excitation heights 85–115 km) during earthquakes. The analysis revealed an increase in mean night-time 557.7 nm emission intensities prior to earthquakes, with a decrease in intensities during post-earthquake days. Preliminary results of a spectral analysis suggest possible changes in spectra (from a few to tens of minutes) of 557.7 nm emission prior to and after earthquakes. The results are compared with those obtained for the earthquakes in the Central Asian region.

Seasonal variation of upper-atmospheric emission in the atomic oxygen 558 nm line over east Siberia

Abstract Upper-atmospheric airglow observations were used to investigate the seasonal variation of upper-atmospheric emission in the atomic oxygen 558 nm [OI] line over the region of East Siberia (52° N, 103° E). There is qualitative agreement with the seasonal variations of 558 nm emission obtained in preceding decades at other mid-latitude stations, as well as with model approximations. Quantitative differences of the seasonal variation of 558 nm emission for the region of East Siberia are considered, which imply a more pronounced autumn maximum and larger values of monthly mean 558 nm emission intensities in the winter months (December–January). An analysis of the factors and phenomena that are responsible for the seasonal variation of 558 nm emission, and a comparison with the wind regime dynamics of the upper mesosphere - lower thermosphere as well as with stratospheric warmings in the region of East Siberia suggests the existence of regional (longitudinal) features in the seasonal variation of 558 nm emission.

Erythemal ultraviolet radiation as deduced from data of ground-based and satellite measurements

A comparative analysis of midday values of direct erythemal radiation (ER) from ground-based measurements at Irkutsk and of values of total ER from satellite data for the period 1999-2001 is carried out. A correlation analysis is made of the ground-based of total ER from satellite data for the period 1999-2001 is carried out. A correlation analysis is made of the ground-based and satellite data for separate months and years, and for the input data set for the entire three-year period. In the analysis of the day-to-day variations we identified periods with a high degree of correlation (0.86-0.99) between ground-based and satellite data, as well as periods with distrubances in the consistency of the variations. We discuss the possible reasons behind the features identified and the differences observed in the ER variations of ground-based measurements and satellite data. In the ground-based measurements we identified an asymmetry of the seasonal ER behavior with respect to the summer solstice, implying an increase of ER-values in the second half-year when compared with the first half-year for the same angular altitudes of the Sun. This feature is more poorly pronounced in the satellite data and is distinguished when only days with clear weather are taken into account. A pronounced seasonal behavior of the ER variation coefficients with large values in the second half-year is pointed out.

Irregular variations of ground-level ultraviolet radiation

We present and analyze the data of daily observations of ground-level near-noon ultraviolet (UV) radiation of the Sun in the wavelength range 295 - 345 nm at Irkutsk (East Siberia, 52 degree(s)N, 104 degree(s)E) for 1998 - 2000. The study revealed an asymmetry of the seasonal variation of UV radiation with respect to the summer solstice, and its dependence on the wavelength in the spectral range under consideration. Irregular variations of ground-level UV radiation, typical of the region, were identified, which depend on the season, and on the selected spectral range. The detected features of the irregular variations are interpreted in terms of the existence of a pronounced annual variation in total ozone content, the variation (during different seasons) of the proportion of the contribution to the attenuation of UV radiation from the Rayleigh and aerosol scattering, the absorption by ozone, and of the specific climatic weather regime in East Siberia.

Variations of the ground-level ultraviolet radiation in East Siberia

Abstract Daily measurements of the ground-level ultraviolet radiation (UVR) for the years 1998–2000 were used to investigate the seasonal UVR variation in the East Siberian region. The study revealed the asymmetry of the seasonal UVR variation with respect to the angular altitudes of the Sun, caused by the seasonal variation of the total ozone content (TOC), and possibly by the presence of the snow cover. Characteristics of the occurrence of short-lasting increases in UVR are considered, which are associated with TOC anomalies and with high atmospheric transparency. Fluctuations of the ground-level UVR with periods of 2.8, 6–13 and 26 days are identified. A study is made of the dependence of the ground-level UVR on solar activity. Statistically significant correlation coefficients with solar activity indices are obtained.

Optical effects of the operation of the onboard engine of the Progress M-17M spacecraft at thermospheric heights

This paper presents the results of optical observations in the active space experiment “Radar-Progress” on April 17, 2013, after switching on the approach-correction engine of the Progress M-17M cargo spacecraft at thermospheric heights (412 km), are presented in this paper. During engine operation, a region of enhanced emission intensity has been recorded. It was presumably related to the scatter of twilight solar emission at the engine exhausts in the cargo spacecraft orbit and, probably to the occurrence of an additional emission in the atomic oxygen line [OI] 630 nm. The maximum observed dimensions of the emission region were ~350 and ~250 km along the orbit and across it, respectively. The velocity of the expansion of the emission region at the first moments after the initiation of engine operation was ~7 and ~3.5 km/s along the orbit and across it, respectively. The maximum intensity of the disturbed region is estimated to be a value equivalent to ~40–60 R within the spectral band of 2 nm. No optical manifestation, which would exceed the natural variations in brightness of the night airglow and which would be related to possible large-scale modification of the ionosphere, was detected in the natural emission lines [O] 557.7 and 630.0 nm in a zone remote from the place of injection of engine exhausts.

Spatial inhomogeneities of erythemal ultraviolet radiation fields

Using satellite (Earth Probe TOMS) measurements of erythemal ultraviolet radiation (EUVR) we examine the global and regional (for Russia) spatial distributions of EUVR. Global distributions of monthly and yearly EUVR doses reveal continental structures and large mountain-masses. An examination of the EUVR distribution for the Russias territory reveals meso-scale inhomogeneities of EUVR fields depending on the region and season under consideration. Our results are in qualitative agreement with earlier findings derived by other authors from investigating global distributions of the total ozone content that is a crucial agency for the supply of EUVR to the ground. We discuss the competing contribution from meteorological (cloud cover, aerosols) and other factors of influence of EUVR in the effects observed. Generally EUVR fields are produced under the influence of many atmospheric factors whose distribution can be affected by orographic conditions, the degree of continentality, circulation processes, and by the physico-geographic properties of the region.

Long-term variations of erythemal ultraviolet radiation in Irkutsk as deduced from satellite measurements

The analysis of temporal variations of erythemal ultraviolet radiation (EUVR) in Irkutsk is given on the basis the data of satellite measurements of solar EUVR by TOMS (Nimbus-7, Earth Probe) processed with the help of special complex of programs for the periods 1979-1992 and 1996-2003. The results of the long-term homogeneous measurement analysis carried out and processed by unified techniques allow establishing climatic norms of different temporal variation scales (inter-seasonal, inter-annual, within the cycle of solar activity). The possible reasons of the observing temporal variations of ground-level EUR in Irkutsk are being discussed.

Wave disturbances in the Earth's atmosphere during the passage of Leonid's meteor stream on November 16-18, 2001

An analysis is made of the disturbances in the atmosphere during the passage of the meteor flow on November 16-18, 2001, based on using simultaneous ground-based measurements of the Earths atmospheric airglow in the 558 nm and 630 nm lines, and in the UV and blue spectral regions, and ground-level microvariations of the pressure, visual observations, and satellite measurements of total electron content variations in the ionisphere. Result of spectral, cross-correlation and wavelet analyses of the measured quantities are presented. In the range of periods corresponding to acoustic-gravity waves, changes in amplitude-frequency characteristics of the variations of the measured quantities are observed in the maximum phase of the meteor flow. We discuss the possible relationship of the recorded dynamics of the variations and intenisty disturbances of the upper atmospheric airglow, total electron content in the ionosphere, and ground-level pressure with the meteor flow. This work was done with support of the RFBR - grant for leading scientific schools of the Russian Federation No.00-15-98509.