HR: 0800h
AN: SM21B-0382    [Abstracts]
TI: Magnetic Flux Pileup and Magnetic Field Dipolarization During Substorm
AU: * Zhang, H
EM: zhanghui@space.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: Cao, X
EM:
AF: School of Earth and Space Science, Peking University, No. 5, Yiheyuan Street, Beijing, 100871 China
AU: Fu, S
EM:
AF: School of Earth and Space Science, Peking University, No. 5, Yiheyuan Street, Beijing, 100871 China
AU: Xiao, C
EM:
AF: The National Astronomical Observatories, CAS, No. 20, Datun Street, Beijing, 100012 China
AU: Zong, Q
EM:
AF: CSP, Boston University, 725 Commonwealth Avenue, Boston, Mas 02215 United States
AU: Liu, Z
EM:
AF: Center for Space Science and Applied Research, CAS, No. 1, Nanertiao, Zhongguancun, Beijing, 100080 China
AU: Cao, J
EM:
AF: Center for Space Science and Applied Research, CAS, No. 1, Nanertiao, Zhongguancun, Beijing, 100080 China
AU: Korth, A
EM:
AF: Max-Planck-Institute for Solar System Research, Max-Planck-Str. 2, Katlenburg-Lindau, 37191 Germany
AU: Frazen, M
EM:
AF: Max-Planck-Institute for Solar System Research, Max-Planck-Str. 2, Katlenburg-Lindau, 37191 Germany
AU: Carr, C
EM:
AF: The Blackett Laboratory, Imperial College, Prince Consort Road, London, SW7 2BZ United Kingdom
AU: Reme, H
EM:
AF: CESR, 9 Avenue du Colonel Roche, Toulouse, F-31028 France
AU: Glassmeier, K
EM:
AF: IGM, TU Braunschweig, Mendelssohnstr. 3, Braunschweig, D-38106 Germany
AB: During the period from July to October in 2004, the orbit apogee of Double Star TC-1 of 13Re located in the magnetotail, which made it possible to survey some basic features of substorm processes in the magnetotail. In the present paper we make a case study of substorm occurring on Sep. 17, 2004. At about 0117 UT FUV WIC on board IMAGE observed an aurora breakup. Almost at the same time the LANL-01A and 90-085 at the geosynchronous altitude detected dispersionless injection of energetic electrons. About 2-3 minutes later a weak dipolarization was seen by NOAA geosynchronous satellite GOES 12. Interestingly, ten minutes before substorm onset, Cluster observed an earthward flow at (-15.00, 2.05, 3.50) Re(GSM). At 0116 UT (one min before onset) TC-1 saw a beginning of magnetic flux pile-up at its position (-10.26, -1.36, 1.01) REGSM, characterized by an increasing of Bz component with almost constant Bx and thermal pressure. At about 0126 UT (9 minutes after onset) TC-1 observed a local dipolarization of the magnetic field which was characterized by a rapid decrease of Bx component and a sharp jump in the thermal pressure, together with a continuous increase of Bz. In the literature, some authors treated the flux pile-up and dipolarization in the tail as a single process named `dipolarization'. However, as TC-1 measurements show in this event, flux pile-up and dipolarization are characterized by completely different signatures. The same feature holds for many other events. Detailed inspections of TC-1 data in this event show that the beginning of flux pile-up was about 10 minutes preceding the dipolarization. Besides, the latter lasted only for about two minutes, whereas the former kept for almost one hour. All these aforementioned differences imply that flux pile-up and dipolarization are two different dynamical processes. Nevertheless, further studies indicate that they are `cause-effect' related: The magnetic flux pileup may lead the field lines with `good' curvature to change to the `bad' ones, further compresses the magnetic field and yields disturbances. These can set up appropriate conditions for development of instabilities and then trigger substorm expansion onset. In summary, this case study seems consistent with the synthesis substorm model of near-Earth neutral line (NENL) and near-Earth current disruption (NECD).
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