HR: 0800h
AN: SM11A-1170    [Abstracts]
TI: Motion of near-Earth neutral line in substorm recovery phase
AU: * Nagata, D
EM: nagata@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakechou, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Machida, S
EM: machida@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakechou, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Ohtani, S
EM: ohtani@jhuapl.edu
AF: Applied Physics Laboratory, Johns Hopkins University, 11100 Johns Hopkins Road, Laurel, MD 20723 United States
AU: Nagai, T
EM: nagai@geo.titech.ac.jp
AF: Department of Earth and planetary Sciences, Tokyo Institute of Technology, 2-12-1,Ookayama,Meguro, Tokyo, 152-8551 Japan
AU: Saito, Y
EM: saito@stp.isas.jaxa.jp
AF: The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshino-dai, Sagamihara, 229-8501 Japan
AU: Mukai, T
EM: mukai@stp.isas.jaxa.jp
AF: The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshino-dai, Sagamihara, 229-8501 Japan
AB: A primary characteristic of the plasma sheet boundary layer(PSBL) is the presence of high speed field-aligned ion beams with abrupt low-speed cutoffs. Onsager et al.[\textit{JGR,96},20,999,1991] proposed a model of the formation of the PSBL which assumed a steady spatially extended source of plasma, together with steady equatorward ExB convection due to reconnection at a downtail neutral line. Elphic et al. [\textit{JGR,100},1857,1995] applied this model to ISEE 2 observations to estimate the downtail distance of the neutral line. The estimated locations were more than 65 $R_E$ downtail from the Earth, which seem to correspond to the distant neutral line(DNL). In this study, we estimated the distance of a near-Earth neutral line(NENL), which is inferred to be formed during substorms, by applying the velocity filter effect model of plasma sheet boundary layer(PSBL). The method was applied to counter-streaming ion beams observed by Geotail during the substorm event at 11:02 UT on Octorber 5, 2000. In the best case,we can estimate the downtail distance of the NENL with an accuracy of 10%. The estimated values range from 20 to 55 $R_E$ downtail, and increased with the total pressure decrease. This is consistent with previous statistical studies [\textit{Nagai et al.,JGR,101},4419,1998;\textit{Miyashita et al.,JGR,108},1353,2003]. In contrast to the past studies, however, our approach allows us to monitor the distance of the NENL continuously and to address its dynamics in the course of substorms.
DE: 2740 Magnetospheric configuration and dynamics
DE: 2748 Magnetotail boundary layers
DE: 2764 Plasma sheet
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting