On the stress balance in flux transfer events

A theoretical discussion is presented of certain aspects of the structure and dynamic of holes in the magnetopause through which magnetic flux connects the magnetosphere with the magnetosheath in the manner describe in the Russell-Elphic model of flux transfer events (FTEs). It is shown that a net current with direction parallel to B for B_y>0 and antiparallel to B for B_y<0 must flow through the hole. This current may provide a natural explanation for the observed helical field observed in FTE flux tubes. If the hole radius, a, is less than a certain critical value, a_crit, it is found that the hole will convect with the ambient plasma flow speed; if a>a_crit, as is expected for most FTEs, the hole may under certain reasonable assumptions move away from the subsolar region (the assumed region of formation of a hole pair) at a speed that exceeds the ambient flow speed and approaches the value expected in steady state reconnection for a>>a_crit. For a>a_crit, reconnection is assumed to occur between flux tube field and the field B_y contained in the magnetopause layer, the result being a flux tube structure consisting of an inner core surrounded by a mantle region which contains reconnected flux and energized plasma.