[23] As a result of morphological and theoretical analysis of the seasonal features of ionospheric storm manifestations at various latitudes of the east Asian region, the following regularities are found:
[24] 1. For the summer storm, an appearance of negative disturbances in the electron concentration is typical both at high and middle latitudes. At low latitudes the disturbances are mainly positive. The sign of the disturbance changes in the vicinity of 30o of geomagnetic latitude.
[25] 2. During the winter storm, positive disturbances were observed in the daytime during the main phase at all the stations considered. At the recovery phase in the daytime, the disturbances are of the negative character at high and middle latitudes. At low latitudes, the disturbances are positive both in the daytime and at night during the entire storm.
[26] 3. In the equinoxes during the main phase of the storm and in the beginning of the recovery period at middle and high latitudes, negative ionospheric disturbances were observed. At low latitudes, both types of disturbances were observed.
[27] 4. The results of model calculations with correction of the MSIS 86 thermospheric model showed that the observed at middle latitudes negative character of an ionospheric storm in summer and positive type in winter can be explained by the corresponding variations in the thermospheric composition.
[28] 5. The available empirical models of auroral precipitations and magnetospheric convection do not make it possible to describe adequately in the scope of a theoretical model of a storm the real structure of the disturbed high-latitude ionosphere. A correction of empirical models of magnetospheric sources provides no significant improvement.
[29] 6. It is shown that at modeling of the response of the midlatitude ionosphere to a geomagnetic storm, one should take into account variations during the storm of the degree of plasmapause filling in, that is, to consider the ionosphere and plasmasphere as a united system.
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