The variation of the Geoeffectiveness of the Recurrent CIRs during their Life Period

Corotating Interaction Regions (CIRs) can cause recurrent geomagnetic storms. Previous case studies of recurrent CIRs, which originate from the same coronal hole on the Sun and periodically cause geospace disturbances, showed that their geoeffectiveness can be quite different. In this paper, the variations of the geoeffectivenss of recurrent CIRs in their whole life will be statistically studied, using the CIR list from Jian et al. [2011]. Among the CIR list, those occurred every 27 days were treated as recurrent CIRs and were put in a group. At last, 304 recurrent CIR groups were obtained from the total 579 CIRs in the list. Among them, 55 groups lasted for at least 3 solar rotations and the longest one lasted for 16 solar rotations. By analyzing the geoeffectiveness of these recurrent CIR groups, it shows that: (1) the geoeffectiveness of recurrent CIRs varies during their whole life, and can be divided into three phases: the enhancement phase, the peak phase, and the decay phase; (2) intense geomagnetic storms are more likely to be caused by CIRs in the medium of their life, then the geoeffectiveness starts to decrease; (3) long lasting CIRs cause intense geomagnetic storms with higher possibility; (4) ICMEs interacted with CIRs can enhance their geoeffectiveness.