Evaluation of substorm models with Cluster observations of plasma flow reversal in the magnetotail

• 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 similar to 19 R-E in the magnetotail during a substorm. oil 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.

Ämnesord

NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

Nyckelord

substorm

current disruption

Physics

Fysik

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