HR: 0800h
AN: SM31B-1231    [Abstracts]
TI: Continuous Lobe Reconnection in the Mid-Tail: Observational Signatures and Relation to Substorm onset
AU: Zhang, H
EM: zhanghui@space.pku.edu.cn
AF: School of Earth and space Sciences, Peking University, Department of Geophysics, Peking University, Beiijng, 100871 China
AU: * Pu, Z
EM: zypu@pku.edu.cn
AF: School of Earth and space Sciences, Peking University, Department of Geophysics, Peking University, Beiijng, 100871 China
AU: Cao, X
EM: cx_octor@pku.edu.cn
AF: School of Earth and space Sciences, Peking University, Department of Geophysics, Peking University, Beiijng, 100871 China
AU: Xiao, C
EM: cjxiao@pku.edu.cn
AF: School of Earth and space Sciences, Peking University, Department of Geophysics, Peking University, Beiijng, 100871 China
AU: Fu, S
EM: suiyanfu@pku.edu.cn
AF: School of Earth and space Sciences, Peking University, Department of Geophysics, Peking University, Beiijng, 100871 China
AB: Magnetospheric substorms represent a global interaction between the solar wind, the magnetosphere, and the ionosphere. Energy extracted from the solar wind is mainly stored in the form of excess magnetic flux in the magnetotail lobes. There is little doubt that reconnection occurs in the magnetotail at some point during substorms. However, whether or not explosive release of this energy is required to cause the substorm and whether reconnection precedes or succeeds expansion onset are still subjects of big debate and controversy. In past three years (2001-2003) Cluster constellation passed through the plasma sheet more than one hundred times. Base on survey of the three yearAŸ’'A+ƒ_TAŸƒ_sA,A›AŸ’'A,A›AŸA›A›ƒ_sAªA.A­AŸƒ_sA,AªAŸ’'A,A›AŸA›A›ƒ_sAªA.A_AŸƒ_sA,A›s four spacecraft data, we have selected 39 continues lobe reconnection (CLR) events. A careful study of these events indicates that the CLR and plasma sheet closed field line reconnection manifest quite differently. The CLR occurs when the IMF is persistently southward (say, for more than a few tens of minutes) and maintains for more than about 20 minutes. It creates a low-density and low-temperature structure with high-speed plasma flows near the central plasma sheet. Quite often the CLRs appear quasi-periodically and in association with the presence of a magnetic storm. Comprehensive investigations have been made in this paper on the relationship between the occurrence of CLRs in the mid-tail and the substorm onsets in the near-Earth region. The 39 CLRs are all found to be corresponding to the appearance of intense substorms. In 37 events the CLRs precede substorms expansion onsets, while other two are opposite. These suggest that tail lobe unloading via CLR is a critical issue for the expansion onset of substorms occurring in persistently southward IMF periods. Nevertheless, this study does not exclude that substorms of other types may have different causes and that dynamical processes in the near-Earth tail are important in triggering the substorm expansion onset.
DE: 7835 Magnetic reconnection
DE: 2744 Magnetotail
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting