HR: 08:30h
AN: SM31A-03    [PDF]
TI: Cluster Observations of a Near-Earth Neutral Line on August 27, 2001
AU: * McPherron, R L
EM: rmcpherron@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567 United States
AU: Baker, D N
EM: Dan.Baker@lasp.colorado.edu
AF: Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309 United States
AU: Kivelson, M G
EM: mkivelson@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567 United States
AU: Khurana, K
EM: kkhurana@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567 United States
AU: Balogh, A
EM: a.balogh@ic.ac.uk
AF: Space and Atmospheric Physics Group, The Blackett Laboratory Imperial College Prince Consort Road, London, SW7 2BW United Kingdom
AU: Reme, H
EM: Henri.Reme@cesr.fr
AF: CESR BP4346, 9 avenue du Colonel Roche, Toulouse, Cedex 04, 31028 France
AU: Dandouras, I
EM: Iannis.Dandouras@cesr.fr
AF: CESR BP4346, 9 avenue du Colonel Roche, Toulouse, Cedex 04, 31028 France
AU: Singer, H
EM: Howard.Singer@noaa.gov
AF: NOAA Space Environment Center, 325 Broadway, Boulder, CO 80305 United States
AU: Donovan, E
EM: eric@phys.ucalgary.ca
AF: Department of Physics and Astronomy, University of Calgary, Calgary, ALB T2N 1N4 Canada
AB: At 0400 UT on August 27, 2001 the Cluster spacecraft located near midnight at 19 Re began to observe a tailward flow with southward magnetic field. This flow persisted for several minutes and then both field and flow reversed to northward and Earthward. The event was associated with a rotation of the magnetic field from its usual orientation along the GSM X-axis to nearly antiparallel to the Y-axis. In a principal axis system the Bx' component changed from +12 nT to -12 nT and then back. As the spacecraft passed downward through Bx' = 0 significant current antiparallel to the magnetic field was encountered. At this time the line containing the field and current pointed roughly 45 from gsm Bx towards dawn. The plasma flow was generally tailward orthogonal to the line containing the field and current. While the spacecraft were in the region of negative Bx' the plasma flow was tailward along X. When the spacecraft returned through Bx' = 0 the current and field were again antiparallel at 45 and the flow was still tailward orthogonal to the current and field. Next the flow rotated 180 becoming Earthward with a duskward component. These observations suggest that an x-line formed Earthward of Cluster releasing a structure that was convected tailward past the spacecraft. This x-line remained Earthward of Cluster for four minutes steadily forcing plasma tailward with imbedded southward magnetic field. The x-line then moved tailward past Cluster rotating the field to northward and the flow to Earthward. These observations become particularly important when placed in the context of substorm activity on this day. A major substorm expansion followed the onset of the x-line signatures by about six minutes.
DE: 2740 Magnetospheric configuration and dynamics
DE: 2744 Magnetotail
DE: 2764 Plasma sheet
DE: 2788 Storms and substorms
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting