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Abstract:
Geomagnetic storms are severe space weather phenomena that affect communication, transportation, navigation, power grid systems and satellite electronic systems. ICMEs and CIRs are the major drivers of storms. Investigating the recovery phase of geomagnetic storms holds pivotal importance in predicting these natural phenomena. We have investigated the fast and slow recovery of extreme storms that occurred in the last three decades. We used exponential, hyperbolic, and linear decay functions to fit the fast and slow recovery of the storms. We observed that exponential and hyperbolic functions are well explained only for fast recovery while slow recovery is well explained by a linear function. Our specific investigation into ICME-induced extreme storm recovery has revealed an extended recovery period in a distinct case, wherein the presence of Alfvén waves during the slow recovery phase suggests their potential role in elongating storm recovery. Additionally, our study of CIR-driven storms, typically of weak to moderate strength, between 1996 to 2016 identified twelve intense storms caused solely by CIRs, with no ICME influence. In 83% of these events, we observed a planar magnetic structure (PMS) during the storm’s main phase. This finding highlights the potential importance of PMS-like quasi-2D magnetic structures in strengthening the Bz component and increasing storm intensity during CIRs.