HR: 1340h
AN: SM13C-1461    [Abstracts]
TI: Evolution of the near-Earth magnetotail associated with substorm expansion onsets
AU: * Miyashita, Y
EM: miyasita@stp.isas.jaxa.jp
AF: Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan
AU: Machida, S
EM: machida@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
AU: Kamide, Y
EM: kamide@rish.kyoto-u.ac.jp
AF: Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto, 611-0011, Japan
AU: Liou, K
EM: Kan.Liou@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, United States
AU: Fujimoto, M
EM: fujimoto@stp.isas.jaxa.jp
AF: Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan
AU: Ieda, A
EM: ieda@stelab.nagoya-u.ac.jp
AF: Solar-Terrestrial Environment Laboratory, Nagoya University, Chikusa-ku, Nagoya, Aichi, 464-8601, Japan
AU: Nagata, D
EM: nagata@kugi.kyoto-u.ac.jp
AF: Department of Geophysics, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
AU: Saito, M
EM: msaito@stp.isas.jaxa.jp
AF: Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan
AU: Shinohara, I
EM: iku@stp.isas.jaxa.jp
AF: Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 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, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan
AU: Saito, Y
EM: saito@stp.isas.jaxa.jp
AF: Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan
AU: Nose, M
EM: nose@kugi.kyoto-u.ac.jp
AF: Data Analysis Center for Geomagnetism and Space Magnetism, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
AU: Christon, S P
EM: spchriston@aol.com
AF: Focused Analysis and Research, 11043 Berrypick Lane, Columbia, MD 21044, United States
AU: Hayakawa, H
EM: hayakawa@stp.isas.jaxa.jp
AF: Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan
AU: Frey, H U
EM: hfrey@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California, Berkeley, 7 Gauss Way, Berkeley, CA 94720, United States
AU: Russell, C T
EM: ctrussel@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, 6843 Slichter Hall, Los Angeles, CA 90024-1567, United States
AU: Singer, H J
EM: Howard.Singer@noaa.gov
AF: Space Environment Center, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder, CO 80305, United States
AB: We have statistically studied substorm-associated evolution of the magnetotail and the inner magnetosphere to understand the triggering mechanism of the substorm expansion onset. In the present study we used ion and magnetic field data from Geotail and magnetic field data from Polar and GOES to cover not only the near-Earth magnetotail but also the inner magnetosphere. A total of 3950 substorm events were determined from auroral breakups observed by the Polar UVI and IMAGE FUV auroral imagers. A few min before auroral onset, the total pressure starts to decrease first in the premidnight tail at X ~ -18 R_E, where electric and magnetic field fluctuations also seem to occur. This location corresponds to the tailward edge of a region of strong magnetic field line stretching that extends from X ~ -8 R_E to X ~ -18 R_E. The plasmoid starts to substantially evolve at X < -20 R_E, simultaneous with the beginning of the dipolarization at X ~ -8 to -9 R_E. The dipolarization region then expands tailward as well as in the dawn-dusk directions and earthward. These observations suggest that, on average, the magnetic reconnection occurs first in the premidnight tail at X ~ -18 R_E just before expansion onset to trigger onset processes. It is still unclear how the magnetic reconnection and the dipolarization are connected.
DE: 2704 Auroral phenomena (2407)
DE: 2723 Magnetic reconnection (7526, 7835)
DE: 2740 Magnetospheric configuration and dynamics
DE: 2744 Magnetotail
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting