Multi-Spacecraft Observation of a High-Speed Flow Event at the Dayside 
Magnetopause for Strong IMF By: A Preliminary Study

Zhang, X., Pu, Z., Cao, X., Wei, Y., Fu, S., Xiao, C., Wang, X., Dunlop, M., 
Zong, Q., Liu, Z., Carr, C., Glassmeier, K., Reme, H., Fazakerley, A.


At about 0330 UT on February 23, 2005, Cluster was located at about
(9.0,1.6,7.0)Re(GSM); the GSM locations of Double Star TC-1 and TC2 at 0430UT
were about (10.4,0.4,2.1)Re and about (0.5,0.1,-1.4)Re in the low-altitude cusp,
respectively. Inside the dayside magnetosheath close to the magnetopause, Bx was
about 0, Bz was positive with the maximum being less than 20nT, and By=-50nT.
During 0320-0340 Cluster four spacecraft were traversing through the
magnetopause and observed pronounced plasma flow in the magnetospheric boundary
layer. The flow speed was over 370 km/s, much higher than the background
magnetosheath flow and directed poleward and duskward. Preliminary analysis
shows that this high-speed flow may possibly manifest a reconnection event. In
the meantime, TC-1 at the low-latitude also observed high-speed flow when the
satellite entered the LLBL for a short time interval. The flow was basically
along the +y-direction and much higher than the background magnetosheath flow.
Interesting enough, just within the time period of Cluster measurement of
high-speed flow, the IMAGE FUV observed both proton and electron aurora
brightening on the duskside of polar ionosphere. One hour later around 0440 UT,
TC-1 was crossing the magnetopause from the magnetosphere toward the
magnetosheath. The spacecraft encountered with high-speed flow in the LLBL and
an FTE in the magnetosheath. Of particular interest are the facts that just in
the time period of TC-1 observation of high-speed flow, TC-2 detected sharp
energetic electron enhancements and the IMAGE FUV also saw both proton and
electron aurora brightening on the duskside of polar ionosphere. In addition,
TC-2 also detected an energetic electron burst at the time when TC-1 encountered
the FTE. Implications of this multi-spacecraft observation of a high-speed flow
event are discussed in this paper. The possible global reconnection pattern at
the dayside magnetopause is also contemplated.

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Fall Meeting, American Geophysical Union, San Francisco, U.S.A., 
5-9 December 2005