Peculiarities of the ionospheric response to geomagnetic storm on 25 September, 1998, in the East-Asian region

摘要

We present the results derived from investigating the ionospheric effects of a large geomagnetic storm on September 25, 1998, based on analyzing the data of ionospheric stations located in the region of East Siberia and the Far East. For the sake of comparison, we used some European stations. In addition to vertical-incidence sounding data, measurements from the Irkutsk incoherent scatter (IS) radar were used. A comparison of the foF2 variations for the two meridians showed that even with a relatively small difference of longitudes (45°, the recovery phase has substantial differences of ionospheric disturbances. The study revealed the critical frequency variations from stations of the Norilsk chain and at Salekhard during the recovery phase of the storm when negative disturbances recurred after positive disturbances. The sign reversal of disturbance in the displacement from the west to the east is difficult to explain, and further investigation is required.