IONOSPHERIC DISTURBANCES DURING GEOACTIVE PERIODS ON OCTOBER-NOVEMBER,2003 AND NOVEMBER,2004
【摘要】：正Investigation of influence of solar and interplanetary events upon the Earth's magnetosphere and ionosphere is the most important problem of solar-terrestrial physics. Despite the fact that a large amount of experimental and theoretical data has been accumulated to this moment there are the definite complications in prediction of solar activity effects in the ionosphere. In the present solar cycle October and November 2003 are characterized by the unusually high solar activity. Within a year this situation is repeated on November 2004. The activity of last event is less one observed in 2003 (three solar flashes of class X against eleven flashes and the geomagnetic storm with Dst=-383 nT against the geomagnetic storm with Dst=-401 nT). However it also can be related by the greatest event not only in the present 23-th solar cycle, but in all period of space observations as well. The ionospheric storm is a complex set of phenomena, which arises as a response to a disturbance of the geospace during magnetospheric storms, and depends on both parameters of interplanetary magnetic field and intensity storm and the coordinates and local time of the observation. In this study we present the results of coordinated ionosphere observations in the Russian-Chinese network during these geoactive periods 2003-2004. For comparison we have also used the data from some stations of the western hemisphere and the measurements from the Irkutsk incoherent scatter radar. It is shown that the periods of total absorption and the blanketing Es layer at the high latitudes and the extended negative disturbances at the middle latitudes typical for geomagnetic storms such intensity were observed in both hemispheres in 2003 and 2004. The first phenomenon were determined by the precipitating auroral particle fluxes, the negative disturbance in F- layer are usually bounded with the change of circulation system and gas content of neutral atmosphere, mainly decreasing of relation [O]/[N2]. Besides at the high latitudes, the initial phase of the storm led to the sharp decrease of the critical frequencies of F2-layer (a breakup of the daily run foF2), which indicated that the main ionospheric trough (MIT) was formed in the daytime and early evening hours. During intense storms in 2003, events typical of the region of the main ionospheric trough were observed at the geomagnetic latitude of 40°. The most interest effect of storm in 2004, which was absent in 2003 was the peak of foF2 in the east hemisphere during the first and second minima of Dst. This peak appeared in the evening hours at the middle latitudes and expanded to the low latitudes and daytime. It is likely to be present traveling ionospheric disturbance (TID) of the atmospheric gravity waves (AGW) type. The peak of foF2 didn't be observed in the western hemisphere. At low latitudes the critical frequencies of F2-layer very fluctuated in amplitude. The differences of ionospheric disturbances in different hemispheres are determined primarily by the difference of local time of geomagnetic storm onset.