HR: 11:25h
AN: SM22A-05    [Abstracts]
TI: Breakdown of the Frozen-in Condition in the Earth's Magnetotail
AU: * Lui, A T
EM: Tony.Lui@jhuapl.edu
AF: JHU/APL, 11100 Johns Hopkins Rd, Laurel, MD 20723, United States
AU: Zheng, Y
EM: YIhua.Zheng@jhuapl.edu
AF: JHU/APL, 11100 Johns Hopkins Rd, Laurel, MD 20723, United States
AU: Reme, H
EM: Henri.Reme@cesr.fr
AF: CESR, 31028 Toulouse Cedex, Toulouse, 4, France
AU: Dunlop, M W
EM: M.W.Dunlop@rl.ac.uk
AF: RAL, Chilton, Didcot, OX11 0QX, United Kingdom
AU: Gustafsson, G
EM: Georg.gustafsson@irfu.se
AF: IRF, S-755, Uppsala, 91, Sweden
AU: Owen, C J
EM: cjo@mssl.ucl.ac.uk
AF: MSSL, University College London, Holmbury, RH5 6NT, United Kingdom
AB: We investigate in detail the breakdown of the frozen-in condition detected by Cluster at the downstream distance of ~19 RE in the midnight sector of the magnetotail during a substorm expansion on 2001 August 22. It is found that the breakdown occurred (1) in a low density environment with moderate to large proton plasma flow and significant fluctuations in electric and magnetic fields, (2) in regions with predominantly dissipation but occasionally dynamo effect, and (3) at times simultaneously at two Cluster satellites separated by more than 1000 km in both X- and Z-directions. Evaluation of the terms in the generalized Ohm's law indicates that the anomalous resistivity contribution arising from field fluctuations during this event is the most significant, followed by the Hall, electron viscosity, and inertial contributions in descending order of importance. This result demonstrates for the first time from observations that anomalous resistivity from field fluctuations (implying kinetic instabilities) can play a substantial role in the breakdown of the frozen-in condition in the magnetotail during substorm expansions. Consideration of several observed features in the breakdown regions indicates that the breakdown occurs in a turbulent site resembling observed features found in current disruption and dipolarization sites.
DE: 2720 Energetic particles: trapped
DE: 2724 Magnetopause and boundary layers
DE: 2728 Magnetosheath
DE: 2748 Magnetotail boundary layers
DE: 2778 Ring current
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting