HR: 1340h
AN: SM33B-0455    [Abstracts]
TI: Average Plasma Vorticity Field in the Near-Earth Plasma Sheet
AU: * Nagata, D
EM: nagata@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, University of Kyoto, KitashirakawaOiwake-cho, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Machida, S
EM: machida@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, University of Kyoto, KitashirakawaOiwake-cho, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Nagai, T
EM: nagai@geo.titech.ac.jp
AF: Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, 152-8551 Japan
AU: Saito, Y
EM: saito@stp.isas.jaxa.jp
AF: Institute of Space and Astronautical Science, Japan Exploration Agency, Yuino-dai, Sagamihara, 229-8510 Japan
AU: Mukai, T
EM: mukai@stp.isas.jaxa.jp
AF: Institute of Space and Astronautical Science, Japan Exploration Agency, Yuino-dai, Sagamihara, 229-8510 Japan
AB: Understanding the processes which generate field-aligned currents in the nightside magnetosphere is one of the important issues in the solar-terrestrial physics. Flow vorticity in the plasma sheet is considered to be one of the sources of the field-aligned currents. In this paper, a two-dimensional pattern of plasma vorticity in the near-Earth plasma sheet (R = 9-30 Re) is derived from long term plasma measurement by the Geotail spacecraft. The Geocentric Solar Wind (GSW) coordinate system is used in this study. We use the data during non-storm periods (symH > -30 nT) to avoid intense magnetospheric disturbances. Fast flows such as bursty bulk flows are also excluded from the database. Vorticity in the vicinity of the Earth is northward (southward) in the dawn (dusk) side. Vorticity in the low-latitude boundary layer is southward (northward) in the dawn (dusk) side due to flow shears. Calculating the vorticity generation rate S (=v · grad Ω) from flow velocity v and vorticity Ω, we found that spatial distribution of S is consistent with the Region1/Region2 current system. The plasma data are also sorted by the interplanetary magnetic field (IMF) direction, and the dependence of vorticity on IMF is also discussed.
DE: 2409 Current systems (2721)
DE: 2431 Ionosphere/magnetosphere interactions (2736)
DE: 2744 Magnetotail
DE: 2764 Plasma sheet
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005