HR: 1340h
AN: SM13A-1114    [Abstracts]
TI: Geotail observations of temperature anisotropies in the cold plasma sheet on the duskside
AU: * Nishino, M N
EM: nishino@stp.isas.jaxa.jp
AF: University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
AU: * Nishino, M N
EM: nishino@stp.isas.jaxa.jp
AF: ISAS/JAXA, 3-1-1 Yoshinodai, Sagamihara, 229-8510, Japan
AU: Fujimoto, M
EM: fujimoto@stp.isas.jaxa.jp
AF: ISAS/JAXA, 3-1-1 Yoshinodai, Sagamihara, 229-8510, Japan
AU: Ueno, G
EM: gen@ism.ac.jp
AF: Institute of Statistical Mathematics, 4-6-7 Minami-Azabu, Minato-ku, Tokyo, 106-8569, Japan
AU: Terasawa, T
EM: terasawa@phys.titech.ac.jp
AF: Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8550, Japan
AU: Maezawa, K
EM: maezawa@stp.isas.jaxa.jp
AF: ISAS/JAXA, 3-1-1 Yoshinodai, Sagamihara, 229-8510, Japan
AU: Mukai, T
EM: mukai@stp.isas.jaxa.jp
AF: JAXA, 1-6-5 Marunouchi, Chiyoda-ku, Tokyo, 100-8260, Japan
AU: Saito, Y
EM: saito@stp.isas.jaxa.jp
AF: ISAS/JAXA, 3-1-1 Yoshinodai, Sagamihara, 229-8510, Japan
AB: To further our understanding of the solar wind entry across the magnetopause under northward IMF, we have studied temperature anisotropies of the two-component protons and electrons in the cold plasma sheet on the duskside. The two-component protons result from mixing of the cold component from solar wind and the hot component of magnetospheric origin, and may be the most eloquent evidence for the transport process across the magnetopause. The cold component occasionally has a strong anisotropy in the dusk flank, and the sense of the anisotropy depends on the observed locations; the parallel temperature is enhanced in the tail flank while the perpendicular temperature is enhanced on the dayside. The parallel anisotropy of electrons is stronger than that of the cold proton component, which is attributed to selective heating of electrons. We further find that strengths of the parallel anisotropies in the tail flank depend on the latitudinal angle of the IMF; strong parallel anisotropies occur under strongly northward IMF. Next we have performed a case study of a duskside Kelvin-Helmholtz (KH) vortices event on 24 March 1995 to investigate the origin of the anisotropies in more detail. The cold proton component occasionally consisted of counter-streaming beams near the current layer in the KH vortical structure. Low-energy bidirectional electron beams or flat-topped electron distribution functions in the direction along the local magnetic field are apparent on the magnetosphere side of the current layer. We discuss that the bidirectionality of electrons and the cold proton component implies magnetic reconnection inside the KH vortical structure. In addition, we suggest selective heating of electrons inside the vortical structure. Comparing temperatures in the magnetosphere-like region inside the vortical structure with those in the cold plasma sheet, we show that further heating is taking place in the cold plasma sheet or on the way from the vortices to the cold plasma sheet. We discuss that both adiabatic heating and wave-particle interactions may be taking place in the vortical structures and the cold plasma sheet.
DE: 2748 Magnetotail boundary layers
DE: 2764 Plasma sheet
DE: 2784 Solar wind/magnetosphere interactions
DE: 7859 Transport processes
DE: 7867 Wave/particle interactions (2483, 6984)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting