Evolution of Kelvin-Helmholtz Activity along the Dusk Flank Magnetopause from Two-point Distant Observations

FOULLON, C.; FARRUGIA, C. J.; GRATTON, F. T.; OWEN, C. J.; TORBERT, R.; FAZAKERLEY, A. N.

Perugia, Italia

Congreso; XXIV IUGG General Assembly; 2007

IAGA (International Association of Geomagnetism and Aeronomy)

Our purpose is to characterise the evolution of the Kelvin-Helmoltz (KH) activity along the flank magnetopause, over the scales at which the disturbances proceed from the dayside to further down the tail. We examine whether the adjacent boundary layer, expected to form as a result of continued KH activity, is then subject to increased turbulence levels and whether it widens from the subsolar point towards the tail. We use two-point distant observations along the dusk flank magnetopause and at low latitudes, from GEOTAIL and CLUSTER, to quantify the intensification of the KH activity between the two sites, in a period of northward interplanetary magnetic field. GEOTAIL is on the dayside (15 MLT) while CLUSTER is tailward of the dusk terminator (19 MLT). We compare growth and power from magnetic field fluctuations as well as the thickness of the low latitude boundary layer. An estimate of the boundary layer thickness at each site is obtained by correlating normal distances to the magnetopause, derived from an empirical solar wind driven model, with a systematic relationship (the "transition parameter") found between the electron number density and the electron temperature at both sites. At the tailward site, the boundary layer supports longer wavelength and is thicker. This result demonstrates the efficiency of the KH instability as plasma transport mechanism.