Association of large geomagnetic storms with halo CMEs and CIRs observed during 1997–2007

摘要

In the present study, we have analysed large geomagnetic storms associated with storm time index (D_st) decrease of more than 100 nT observed during 1997–2007 and found 90 geomagnetic storms falling in our selection criteria. We have analyzed the association of the above selected 90 large geomagnetic storms with three types of solar drivers: single front-side halo CME (S-type), multiple front-side halo CMEs (M-type) and corotating interaction region, CIR (C-type). It is found that 58% storms were caused by single front-side halo CME (S-type), whereas 30% storms were caused by multiple front-side halo CMEs (M-type). Rest 12% storms were caused by corotating interaction region (CIR). We find that there is an east-west asymmetry and north-south asymmetry as well. We have also shown the association of the selected 90 large geomagnetic storms with three types of surface source region: active region, quiet region and coronal holes. We find that 62% storms were caused by active region whereas 10% storms were caused by quiet region. 12% storms were caused by coronal holes. Surface source region of rest 16% storms are unknown due to data gap.