Intense (SYM - H 6<-100 nT ) geomagnetic storms induced by planar magnetic structures in co-rotating interaction regions

Abstract

Generally, Co-rotating Interaction Region (CIR) induced geomagnetic storms are weak to moderate in magnitude. Moreover, CIRs can also drive intense storms when they are coupled with an ICME or other interplanetary structures. Here, we investigated all intense (SYM H 6 100 nT ) geomagnetic storms caused by CIRs from the years 1996 to 2016. We found 12 intense storms that were solely caused by CIRs, i.e., without any component of ICME. We observed the evolution of a planar magnetic structure (PMS) in 10 CIR events i.e. 83% during the storm’s main phase. It suggests that PMS-like quasi-2D magnetic structures might play a significant role in strengthening the Bz component, which causes the intensification of the storm during CIR transit.