IONOSPHERIC EFFECTS OF THE MARCH 13, 1989 MAGNETIC STORM AT SUBAURORAL REGION

Ionograms and magnetograms at Great Wall (62 degrees 13'S, 58 degrees 58'W), Antarctica, were used to study the ionospheric effects of the M arch 13, 1989 magnetic storm in sub-auroral locations. The virtual hei ght of the F region (h'F) increased and the critical frequency (f(o)F( 2)) decreased rapidly just after the storm sudden commencement (S SC). Then the spread F appeared and lasted about five hours. During the ma in phase of the magnetic storm the ionosphere encountered severe absor ptions, but large enhancements in h'F and associated depressions in f( o)F(2) sometimes were still observed. On the second and third nights a fter the SSC auroral type sporadic E and night E layers were observed, showing peak electron densities as high as 7.5 x 10(5) el cm(-3). The causes of these phenomena are discussed. Behaviours of h'F and f(o)F( 2) from four ionosonde stations in the same longitude sector (Great Wa ll, Port Stanley, Cachoeira Paulista and Fortaleza) show that the high er the station's latitude is, the more severe absorptions occur, and t he longer the depressions of f(o)F(2) last.