Magnetic island formation between large-scale flowvortices at an undulating postnoon magnetopause fornorthward interplanetary magnetic field

摘要

[1] Time History of Events and Macroscale Interactions during Substorms multispacecraftobservations are presented for a —2-h-long postnoon magnetopause event on 8 June 2007that for the first time indicate that the trailing (sunward) edges of Kelvin-Helmholtz (KH)waves are commonly related to small-scale <0.56 R_Emagnetic islands or flux transfer events (FTE) during the growth phase of these surface waves. The FTEs typically show acharacteristic bipolar BN structure with enhanced total pressure at their center. Most of thesmall-scale FTEs are not related to any major plasma acceleration. TH-A observations ofone small FTE at a transition from the low-latitude boundary layer (LLBL) into a magnetosheath plasma depletion layer were reconstructed using separate techniques thattogether confirm the presence of a magnetic island within the LLBL adjacent to themagnetopause. The island was associated with a small plasma vortex and both featuresappeared between two large-scale (~1 R_Elong and 2000 km wide) plasma vortices. Wepropose that the observed magnetic islands may have been generated from a time-varyingreconnection process in a low ion plasma beta (β_i< 0.2) and low 8.3° field shearenvironment at the sunward edge of the growing KH waves where the local magnetopausecurrent sheet may be compressed by the converging flow of the large-scale plasma vorticesas suggested by numerical simulations of the KH instability.