Evaluation of substorm models with Cluster observations of plasma flow reversal in the magnetotail |
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Authors: | ATY Lui Y Zheng H Rème MW Dunlop G Gustafsson |
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Institution: | 1. John Hopkins University, Applied Physics Laboratory, 11100 John Hopkins Road, Laurel, MD, USA;2. CESR, BP4346, 31028 Toulouse Cedex 4, Toulouse, France;3. Space Science and Technology Department, RAL, Chilton, Didcot, Oxfordshire OX11 0QX, UK;4. Swedish Institute of Space Physics, Uppsala Division, S-755 91 Uppsala, Sweden |
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Abstract: | We evaluate two prevailing substorm models with an event of plasma flow reversal from tailward to Earthward detected by Cluster at the downstream distance of ∼19 RE in the magnetotail during a substorm on August 22, 2001. We use the unique capability of Cluster measurements in determining gradients to examine the associated current density, Lorentz force, and current dissipation/dynamo term. In association with plasma flow reversal, it is found that (1) there was no clear quadrupole magnetic perturbation signature, (2) the x-component of the Lorentz force did not change sign, (3) the y-component of the product of the current density and the electric field was occasionally negative indicative of a dynamo effect, and (4) the timing sequence of flow reversal from the Cluster configuration did not match tailward motion of a single plasma flow source. These observations are consistent with the near-Earth initiation model for substorms with multiple current disruption sites moving progressively tailward near the late stage of substorm expansion. |
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Keywords: | Substorm Current disruption |
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