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Recent work has shown that solar wind-magnetosphere coupling is moreefficient for CIR-driven events than for CME-driven events. The studyherein looks into the individual physical parameters of Corotating Interaction Regions (CIRs) and Coronal Mass Ejections (CMEs) and looks to isolate particular characteristics that leads to greater coupling ofenergy from the solar wind into the magnetosphere for certain classesof magnetic storms. While it is clear that these two types of events are distinct in their outcome, it is not known what in the nature of the events leads to these different results. The variation level in the z-component of the Interplanetary Magnetic field (IMF) and the Alfvénic Mach number one hour prior to the onset of a CIR or CME event are investigated as possiblyrelated to the coupling efficiency. While there was no significantcorrelation between any particular characteristic and energy coupling efficiency, the most promising result came from the Alfvénic Mach number and its effect on the energy efficiency of the storm main phase. The Alfvénic Mach numbers of CIR and CME events had the strongest connection to the main phase energy efficiency. More study is needed on the connection between the Alfvénic Mach number as it relates to energy efficiency. Different or combinations of characteristics of these storms may also shed more light on the necessary conditions for a more geoeffective event.

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Journal of the Southeastern Association for Research in Astronomy