Solar wind parameters and geomagnetic indices for four different interplanetary shock/ICME structures

Interplanetary shocks associated with coronal mass ejections (CMEs) have very profound effects on geomagnetic storms. In order to investigate the role of the interplanetary shock properties and pre-conditions, we present a statistical study of 280 interplanetary shocks and their associated geomagnetic activities during 1998-2007. The results show that perpendicular shocks can cause more intense geomagnetic activities compared with parallel ones under the same IMF pre-condition. Through a southward IMF pre-condition, interplanetary shocks and driven ICMEs can intensify geomagnetic storms significantly. It is revealed that interplanetary shocks would intensify negative IMF B-z pre-condition by a factor of 3 to 6. This effect would enhance geomagnetic storms greatly. The result shows that there are 74% of intense (D-st <= -100 nT) and 69% of super (D-st <= -200 nT) geomagnetic storms related to a negative IMF B-z pre-condition.