Plasma sheet thinning due to loss of near-Earth magnetotail plasma

TL;DR

This study extends a 1D plasma sheet thinning model to 2D and 2D with magnetic fields, revealing that interactions with the lobes significantly influence thinning dynamics, challenging previous assumptions of the Current Disruption model.

Contribution

It introduces a multi-dimensional plasma sheet model showing the importance of sheet-lobe interactions in thinning, which were absent in earlier 1D models.

Findings

Rarefaction wave weakens in 2D, stopping propagation.

Plasma sheet thinning persists in 2D with magnetic fields despite wave loss.

Sheet-lobe interactions dominate thinning dynamics, contradicting 1D assumptions.

Abstract

A one-dimensional model for thinning of the Earth's plasma sheet [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. A rarefaction wave, which is a signature component of the CD model, is generated with an initial disturbance. In the 1D gas model, the rarefaction wave propagates tailward at sound velocity and is assumed to cause thinning. Extending to a 2D gas model of a simplified plasma sheet configuration, the rarefaction wave is weakened, and the thinning ceases to propagate. Extending further to a 2D plasma model by adding magnetic field into the lobes, the rarefaction wave is quickly lost in the plasma sheet recompression, but the plasma sheet thinning is still present and propagates independently at a slower velocity than a 1D model suggests. This shows that the dynamics of plasma sheet thinning may be dominated by sheet-lobe interactions that are absent from the 1D model and may not support the behaviour assumed by the CD model.