On the geomagnetic effects of solar wind interplanetary magnetic structures

We present in this work a statistical study of the geoeffectiveness of the solar wind magnetic interplanetary structures over the entire observational period (1964–2003). The structures studied were magnetic clouds (MCs, 170 events), corotating interaction regions (CIRs, 727 events) and interplanetary shocks (830 events). The geoeffectiveness was assessed in terms of the geomagnetic index Kp , AE , and Dst peak values within 2 days after the interplanetary structure had passed near Earth's orbit. Frequency distributions were obtained that give the probability of every interplanetary structure being followed by intense, moderate, weak, or quiet (none) magnetic activity levels. The knowledge of probability distribution is important in schemes to forecast space weather conditions after the detection, by in situ solar wind observations, of an interplanetary structure approaching Earth. We observed that magnetic clouds are more efficient than shocks or CIRs in producing all the geomagnetic activity disturbances; CIRs are themselves more geoeffective as measured by the AE activity. We have confirmed that compound structures (shocks plus MCs) are more geoeffective in every type of magnetospheric activity than isolated structures.