Articles | Volume 17, issue 5
Ann. Geophys., 17, 604–612, 1999

Special issue: Solar System Plasmas

Ann. Geophys., 17, 604–612, 1999

  31 May 1999

31 May 1999

Sausage mode instability of thin current sheets as a cause of magnetospheric substorms

J. Büchner and J.-P. Kuska J. Büchner and J.-P. Kuska
  • Max-Planck-Institute für Aeronomie, D-37191 Katlenburg- Lindau, Germany
  • Correspondence to: J. Büchner, e-mail:

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)

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