A STUDY OF IONOSPHERIC ELECTRON-DENSITY DEVIATIONS DURING 2 GREAT STORMS

A large foF2 data base has been collected for the two great storms occ urring in March and October 1989. Plots of foF2 deviations versus time and latitude show the large depressions cannot be caused by a composi tion change alone; the storm induced dynamo electric field must also p lay an important role, especially for low latitudes. The observed iono spheric response is hemispherically asymmetric, with the autumnal hemi sphere suffering a longer lasting, more latitudinally extended, and de eper depression.