HR: 10:50h
AN: SM52A-03    [Abstracts]
TI: Detection of Rolled-up Kelvin-Helmholtz Vortices From Single-Spacecraft Data
AU: * Hasegawa, H
EM: hiroshih@geo.titech.ac.jp
AF: Tokyo Institute of Technology, I2-34, 2-12-1 Ookayama, Meguro, Tokyo, 152-8551 Japan
AU: Fujimoto, M
EM: fujimoto@geo.titech.ac.jp
AF: Tokyo Institute of Technology, I2-34, 2-12-1 Ookayama, Meguro, Tokyo, 152-8551 Japan
AU: Takagi, K
EM: ktakagi@geo.titech.ac.jp
AF: Tokyo Institute of Technology, I2-34, 2-12-1 Ookayama, Meguro, Tokyo, 152-8551 Japan
AU: Reme, H
EM: henri.reme@cesr.fr
AF: Centre d'Etude Spatiale des Rayonnements, 9 Avenue Colonel-Roche, BP 4346, Toulouse, 31028 France
AU: Saito, Y
EM: saito@stp.isas.jaxa.jp
AF: Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510 Japan
AU: Mukai, T
EM: mukai@stp.isas.jaxa.jp
AF: Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510 Japan
AB: Recent numerical simulation studies show that plasma mixing is inevitably achieved as soon as the Kelvin-Helmholtz instability (KHI), which can become unstable along the flank magnetopause, has grown nonlinearly to form highly rolled-up vortices. Thus, identification of the rolled-up KH vortices with in situ measurements is an important task as a step to establish the mechanism of transporting solar wind plasmas into the magnetosphere and conditions under which the vortices can be generated. In the present study, we show that the rolled-up vortices can be detected even in single-spacecraft measurements of the bulk plasma parameters. Numerical simulations of the KHI indicate that the low-density, magnetospheric plasma is accelerated, within a highly rolled-up KH vortex, to have an anti-sunward velocity higher than the magnetosheath flow. This high-speed and low-density plasma can be seen only after a vortex is rolled up, and even when the vortices have collapsed or coalesced, thus this signature can be used as an indicator of the roll-up. This signature was indeed found in the Cluster multi-spacecraft measurements of the rolled-up vortices at the dusk flank magnetopause [Hasegawa et al., Nature, 430, p.755, 2004]. By use of this indicator, we have searched for rolled-up vortices in observations by the Geotail spacecraft in the flanks which show quasi-periodic plasma and field perturbations in the boundary layer, possibly associated with the KHI. As a result, it was found that the vortices do roll up on both dawn and dusk sides and that such vortices events are not rare under northward IMF conditions. Based on this Geotail data survey, we discuss the relationship between the roll-up and plasma mixing in the boundary layer.
DE: 2724 Magnetopause and boundary layers
DE: 2748 Magnetotail boundary layers
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 7839 Nonlinear phenomena (4400, 6944)
DE: 7859 Transport processes
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005