Intensity variations in red line of atomic oxygen emission were analyzed using the ionosphere-plasmasphere coupling model. These variations were caused by precipitation of energetic electrons from the magnetosphere during the 20 November 2003 geomagnetic storm. The findings were compared to the optical data measured in Geophysical observatory of the ISTP SB RAS (520 N, 1030 E).
A numerical model of the ionosphere has been used to study the dependence of night airglows in red and green lines of atomic oxygen on characteristics of precipitating electrons which can substantially affect conditions in the mid-latitude ionosphere during magnetic storms. It has been established that the precipitations are able to indirectly generate airglow in red and green lines of atomic oxygen by increasing rates of ion formation and heating of thermal electrons, which causes an increase in the rate of dissociative recombination and thermal-electron-collision excitation of the <sup>1</sup>D and <sup>1</sup>S levels.
We studied the 557,7 and 630-nm atomic oxygen emission responses to the solar wind sharp variations caused by shocks. For the analysis, were used optical and geomagnetic data for the Eastern Siberia and interplanetary magnetic field and solar wind data. The considered emission intensity was found to increase for some cases, whereas, in other cases, there were no responses during sharp variations in solar wind plasma speed and density. The presence or absence of the responses in the emissions was shown to be not related to the disturbance amplitude of the solar wind parameters. We suggested that the emission intensity increase might be caused by electron precipitation from the magnetic trap during the interaction between the solar wind shock and the magnetosphere.
The results of studies of the ionospheric response to solar flares are presented. The results are based on the observations
of GPS signals and at incoherent scatter radars and on theoretical calculations. Analyzing the GPS data, the method
based on a partial "shadowing" of the atmosphere by the Earth was used. This method made it possible to estimate the
value of the electron content variations in the topside ionosphere during the solar flare on 14 July 2000. We obtained that
according to the GPS data at altitudes of the topside ionosphere (h > 300 km) a flare is able to cause a decrease of the
electron content. Similar effects of formation of a negative disturbance in the ionospheric F region were observed also
during the solar flares on 21 and 23 May 1967 by the Arecibo radar. Using the theoretical model of ionosphere--
plasmasphere interaction, we study in this paper the mechanism of formation of negative disturbances in the topside
ionosphere during solar flares. It is shown that the intense transport of O+ ions into the above-situated plasma caused by
a sharp increase in the ion production rate and thermal expansion of the ionospheric plasma is a cause of the formation of
the negative disturbance in the electron concentration in the topside ionosphere.