Magnetosphere Seminars

May 21, 2013 – “The Effects of Extreme Density Asymmetry on Magnetopause Reconnection Exhausts at High Latitudes”

Speaker:Frederick Wilder (LASP)
Date:Tuesday, May 21, 2013
Time:4:00 PM
Location:LASP Space Science Building, room N248 upstairs. Map

Seminar Abstract:

When the interplanetary magnetic field (IMF) is northward, reconnection between the IMF and geomagnetic field occurs at high latitudes, poleward of the cusp. In this region, there is a large flow-shear and density asymmetry across the magnetopause current sheet. We present observations from one magnetopause crossing by two of the Cluster spacecraft on 27 December 2005. Minimum variance analysis is performed in order to show that the exhaust associated with reconnection poleward of the cusp lies earthward of the magnetopause. This is in agreement with theory and simulations of asymmetric reconnection that predict the fastest portions of the reconnection exhaust will flow on the high Alfvén speed side of the current sheet. We also show that using a hybrid plasma density from asymmetric reconnection theory (e.g. Cassak and Shay, 2007) as opposed to the magnetosheath plasma density for the reference plasma density improves agreement between the velocity observations and the Walén prediction that the exhaust will be Alfvénic in the deHoffmann-Teller frame. Additionally, we show that the effect of the large density asymmetry dominates the effects of the flow shear and the guide field on the exhaust for this case.