HR: 0800h
AN: SM21B-0381    [Abstracts]
TI: TC-1 and Cluster Observation of Substorm Dipolarization on Sep 14, 2004
AU: * Cao, X
EM: cx_octor@pku.edu.cn
AF: School of Earth and Space Science, Peking University, No. 5, Yiheyuan Street, Beijing, 100871 China
AU: Pu, Z
EM: zypu@pku.edu.cn
AF: School of Earth and Space Science, Peking University, No. 5, Yiheyuan Street, Beijing, 100871 China
AU: Zhang, H
SM21B-0381 AF: School of Earth and Space Science, Peking University, No. 5, Yiheyuan Street, Beijing, 100871 China
AU: Fu, S
SM21B-0381 AF: School of Earth and Space Science, Peking University, No. 5, Yiheyuan Street, Beijing, 100871 China
AU: Xiao, C
SM21B-0381 AF: The National Astronomical Observatories, CAS, No. 20, Datun Street, Beijing, 100012 China
AU: Zong, Q
SM21B-0381 AF: CSP, Boston University, 725 Commonwealth Avenue, Boston, Mas 02215 United States
AU: Liu, Z
SM21B-0381 AF: Center for Space Science and Applied Research, CAS, No. 1, Nanertiao, Zhongguancun, Beijing, 100080 China
AU: Cao, J
SM21B-0381 AF: Center for Space Science and Applied Research, CAS, No. 1, Nanertiao, Zhongguancun, Beijing, 100080 China
AU: Korth, A
SM21B-0381 AF: Max-Planck-Institute for Solar System Research, Max-Planck-Str. 2, Katlenburg-Lindau, 37191 Germany
AU: Frazen, M
SM21B-0381 AF: Max-Planck-Institute for Solar System Research, Max-Planck-Str. 2, Katlenburg-Lindau, 37191 Germany
AU: Carr, C
SM21B-0381 AF: The Blackett Laboratory, Imperial College, Prince Consort Road, London, SW7 2BZ United Kingdom
AU: Reme, H
SM21B-0381 AF: CESR, 9 Avenue du Colonel Roche, Toulouse, F-31028 France
AU: Glassmeier, K
SM21B-0381 AF: IGM, TU Braunschweig, Mendelssohnstr. 3, Braunschweig, D-38106 Germany
AB: We study the substorm depolarization occurring from 1730 to 1930 UT on Sep 14, 2004 based on DSP TC-1, Cluster and Polar data combined with the aurora and geosynchronous energetic particle measurements and ground-based magnetic field observations. During this time period the IMF is continuously southward. At about 1803 UT Cluster observed signatures of continuous lobe reconnection in the tail (Cao et al., 2005; Zhang et al., 2005; Pu et al., 2005). The ground-based magnetometer records indicate that at about 1823UT, Pi2 pulsations started on the magnetic field D-component in the mid-latitudes. IMAGE FUV WIC observation shows that an aurora breakup took place at almost the same time. Two minute later, energetic electron injection was observed by LANL-02A in the pre-midnight sector at geostationary orbit. At about 1827UT TC-1, which was located at (-10,-2, 0) Re (GSE) in the near-Earth tail, saw a sharp decrease of magnetic Bx component, accompanied by sudden increases in both ion temperature and thermal pressure. About 23 minutes later at about1850UT, the same signatures as observed by TC1 were observed by Cluster at (-16, 1, 3) Re (GSE) in the mid-tail. Meanwhile, POLAR, which was located much higher and more close to the Earth at (-7.5, 3.5, -4.0) Re (GSE), saw a sudden change in the elevation of the magnetic field at about 1855UT. Aforementioned time sequence of substorm activities indicates that the expansion onset took place at about 1823UT and TC-1 and Cluster observed dipolarization (tail expansion) 4 and 27 minutes later, respectively. The wavelet analysis shows that the wave profiles of tail expansion structures seen by TC-1 and Cluster both were very similar. Further more, the power analysis illustrates that they both gad a characteristic period peaked at about1.3-1.5min, almost identified to that of observed mid-latitude Pi2 pulsations. This means that tail expansion was propagated from source region in the near-Earth tail to the mid-tail. Detailed calculations imply that the source of the dipolarization was situated at X=-7.7 Re to -8.6 Re and the propagation speed was about 30km/s. A substorm paradigm is proposed to explain the observations in this substorm event: Earthward flow produced by lobe reconnection in the mid-tail created favorable conditions for substorm initiation in the near-Earth; after the expansion onset the dipolarization front propagates down to the tail.
DE: 2700 MAGNETOSPHERIC PHYSICS (6939)
DE: 2744 Magnetotail
DE: 2764 Plasma sheet
DE: 2788 Magnetic storms and substorms (7954)
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005