Convection Transients in the Polar Cap During Substorms

J. Quinn, G. Paschmann, E. Georgescu, H. Vaith, H. Frey

We report transient convection signatures during substorms, seen by the
Cluster satellites at about 7 RE on field lines mapping to the central polar
cap, using data from EDI and FGM on Cluster, and WIC on IMAGE.  In these
events, typically lasting 1-3 minutes, the Ygse component of electric field
(corresponding to anti-sunward polar cap convection) drops from a
quasi-steady value of a few mV/m, to zero or slightly negative values, and
then returns to the quasi-steady level.  At the same time the magnetic field
shifts to a less "tailward" direction.  We interpret these events as part of
the global reconfiguration associated with substorms.

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Fall 2002 Meeting of the American Geophysical Union
San Francisco, CA, USA, 6-10 December 2002