Loss of the Rarefaction Wave during Plasma Sheet Thinning

A one-dimensional model for plasma sheet thinning [J. K. Chao et al., Planet. Space Sci. 25, 703 (1977)] according to the Current Disruption (CD) model of auroral breakup is extended to two dimensions. An initial disturbance generates a rarefaction wave. In the 1D model the rarefaction wave propagates tailward at sound velocity, which is regarded as a signature of the thinning. However, in the MHD simulation of the 2D model the rarefaction wave is quickly lost in the plasma sheet recompression, while the thinning continues propagating at a slower velocity. This shows that the dynamics of plasma sheet thinning may be dominated by sheet-lobe interactions that are absent from the 1D model.