Cluster Electron Cusp Dispersions and IMAGE Proton Auroras as Evidence for
Continuous Merging at the Magnetosphere

D.E. Wendel, P H. Reiff, A. Fazakerley, J. Bosqued, S. Mende, M.L. Goldstein,
J.D. Winningham


Whether magnetic reconnection at the earth is intrinsically non-steady is still
a controversial question. Some authors have made a case for a pulsed merging
process, with 1 minute of active reconnection followed by 8 minutes without
merging. To pursue this issue, we examine Cluster cusp crossings for evidence of
ongoing electron dispersion. Because electrons disperse very rapidly before
becoming trapped with dispersing ions, their dispersion indicates contact with a
field line that is still actively reconnecting. The detection of electron
dispersions on multiple satellite cusp crossings, during periods of steady IMF
and ideal inter-spacecraft spacing (less than 8 minutes and greater than 1
minute), would support a more continuous merging process. A statistical estimate
of the number of Cluster cusp crossings with electron dispersions may serve as a
proxy, in the absence of ideal inter-spacecraft spacing and extended periods of
steady IMF. Moreover, SI-12 proton aurora data supplement Cluster electron and
ion data in tracking the presence of an active merging sight.

_______________ 
Presentation, Fall Meeting, American Geophysical Union, San Francisco, USA, 
8-12 December 2003