An investigation of the association between steady magnetospheric convection and CIR stream interfaces

It has been postulated that steady magnetospheric convection (SMC), a mode of response of the Earth's magnetosphere to solar wind driving, is caused by balanced day and night side reconnection. We investigate this possibility with a statistical study of return flows in the magnetotail during SMC using the THEMIS mission. Between December 2007 to April 2009, 153 events were identified. We find flows greater than 100 km/s throughout the magnetotail but no distinct pattern of flow channels. SMC occurrence is compared with that of stream interfaces (SI) at the center of corotating interaction regions. “Frequent” SMCs are observed ±1 day around the SI, and “infrequent” 3 to 1.5 days before the SI. The typical solar wind parameters in the frequent interval are higher than expected from previous studies. We found that rectified solar wind electric field steadiness predicts that SMC will occur when this is smaller than average.