|
|
 |
|
|
Ann. Geophys., 17, 604-612, 1999
www.ann-geophys.net/17/604/1999/
© European Geosciences Union 1999
Sausage mode instability of thin current sheets as a cause of magnetospheric substorms
J. Büchner and J.-P. Kuska
Max-Planck-Institute für Aeronomie, D-37191 Katlenburg- Lindau, Germany
Correspondence to: J. Büchner, e-mail: buechner@linmpi.mpg.de
Abstract. Observations have shown that, prior to
substorm explosions, thin current sheets are formed in the plasma sheet of the
Earth's magnetotail. This provokes the question, to what extent current-sheet
thinning and substorm onsets are physically, maybe even causally, related. To
answer this question, one has to understand the plasma stability of thin current
sheets. Kinetic effects must be taken into account since particle scales are
reached in the course of tail current-sheet thinning. We present the results of
theoretical investigations of the stability of thin current sheets and about the
most unstable mode of their decay. Our conclusions are based upon a non-local
linear dispersion analysis of a cross-magnetic field instability of Harris-type
current sheets. We found that a sausage-mode bulk current instability starts
after a sheet has thinned down to the ion inertial length. We also present the
results of three-dimensional electromagnetic PIC-code simulations carried out
for mass ratios up to Mi / me=64. They
verify the linearly predicted properties of the sausage mode decay of thin
current sheets in the parameter range of interest.
Key words. Magnetospheric physics (plasma waves and
instabilities; storms and substorms) · Space plasma physics (magnetic
reconnection)
Full Article in PDF (895 KB) |
|
|
