Local influence of magnetosheath plasma beta fluctuations on magnetopause reconnection
- 1Swedish Institute for Space Physics, P.O. Box 537, 751 21 Uppsala, Sweden
- 2University of Toulouse, UPS, CESR, 9 avenue colonel Roche, 31028 Toulouse cedex 4, France
- 3CNRS, UMR5187, 31028 Toulouse, France
- *now at: Finnish Meteorological Institute, PL 503, 00101 Helsinki, Finland
Abstract. We present observations from two subsolar Cluster magnetopause crossings under southward interplanetary magnetic field and strong mirror mode fluctuations in the magnetosheath. In both events the reconnection outflow jets show strong variations on the timescale of one minute. We show that at least some of the recorded variations are truly temporal, not spatial. On the same timescale, mirror mode fluctuations appear as strong magnetic fluctuations in the magnetosheath next to the magnetopause. This suggests that mirror modes can cause the variations either through modulation of continuous reconnection or through triggering of bursty reconnection. Using a theoretical scaling law for asymmetric reconnection we show that modulation of reconnection at a single x-line can explain the observations of the first event. The second event cannot be explained by a single modulated x-line: there the evidence points to patchy and bursty reconnection.