THE IMF AND ITS ASSOCIATED GEOMAGNETIC αα INDEX AND STORM

The influences of the interplanetary magnetic field (IMF) total intensity Bandits sector boundary on the magnetic field of the Earth are investigated by examination of the maximum αα indices during geomagnetic storms. The stroms are classifiedinto three types according to their different linear'correlations between the IMFandthe αα indices. Each type of the storms has its characteristics in association with theappropriate solar wind parameters. There are two geomagnetic effects in response tothe two spiral IMFsector boundaries passing the Earth. It seems that the αα indexmay take the precedence over others in the study of solar--terrestrial couplings.