Generation and properties of in vivo flux transfer events

Abstract

Of the 3701 flux transfer event signatures that we identified in THEMIS data between May and October of 2007 and 2008 at low-latitudes on the magnetopause, 41 were distinctive in that the north-south flow components reversed direction during the ∼1 min required for THEMIS spacecraft to traverse the structure. We have ruled out the possibility that these 41 "flow reversal events" (FREs) were single X-line structures in motion, and confirmed from their field and plasma properties that they indeed were flux ropes. We have interpreted the plasma flow reversal as evidence that we observed the flux ropes while they were being generated by a pair of X-lines that developed in sequence through component merging, a process that seems to play a significant role in forming flux ropes. Our analysis, which applies only to low latitude flux ropes, provides evidence to modify the updated multiple X-line reconnection scenario with component merging as the dominant associated reconnection process.