Spatial distribution of rolled up Kelvin-Helmholtz vortices at Earth's dayside and flank magnetopause
Berchem, J.; Escoubet, C. P.; Eastwood, J. P.; Lavraud, B.; Wild, J. A.; Fazakerley, A. N.; Hasegawa, H.; Dunlop, M. W.; Volwerk, M.; Frey, H. U.; Bogdanova, Y. V.; Shen, C.; Soucek, J.; Taylor, M. G. G. T.; Pu, Z. Y.; Wang, J.; Masson, A.; Laakso, H.; Borg, A. L.; Shi, J. K.; Sibeck, D. G.; Phan, T.; Panov, E. V.; Constantinescu, O. D.
Netherlands, Japan, France, United States, United Kingdom, Austria, Romania, Czech Republic, China
Abstract
The Kelvin-Helmholtz Instability (KHI) can drive waves at the magnetopause. These waves can grow to form rolled-up vortices and facilitate transfer of plasma into the magnetosphere. To investigate the persistence and frequency of such waves at the magnetopause we have carried out a survey of all Double Star 1 magnetopause crossings, using a combination of ion and magnetic field measurements. Using criteria originally used in a Geotail study made by Hasegawa et al. (2006) (forthwith referred to as H2006), 17 candidate events were identified from the entire TC-1 mission (covering ~623 orbits where the magnetopause was sampled), a majority of which were on the dayside of the terminator. The relationship between density and shear velocity was then investigated, to identify the predicted signature of a rolled up vortex from H2006 and all 17 events exhibited some level of rolled up behavior. The location of the events had a clear dawn-dusk asymmetry, with 12 (71%) on the post noon, dusk flank suggesting preferential growth in this region.