Stability of a thick two-dimensional quasineutral sheet

TLDR

The thick quasineutral sheet configuration permits adiabatic electron motion, consistent with trapped‑electron behavior predicted by the model. The study investigates the stability of a two‑dimensional thick quasineutral sheet model with a finite normal magnetic field in collisionless plasma. A general formalism for arbitrary magnetic configurations is developed and applied to parabolic and magnetic island topologies. The kinetic analysis shows that ion linear tearing modes are suppressed by a compressibility effect from perturbed fields interacting with adiabatic electrons, links this to the MHD energy principle, and indicates that nonlinear tearing modes can enter an explosive phase.

Abstract

The stability of a two-dimensional magnetic model of a thick quasineutral sheet including a small but finite normal magnetic field component is studied in a collisionless plasma. Such a magnetic configuration allows an adiabatic motion for electrons which are trapped in good agreement with the thick sheet model. A detailed kinetic study of the energy balance shows that the ion linear tearing mode instability is suppressed by the interaction between the perturbed electromagnetic field and the adiabatic electron motion; this interaction leads to a ‘‘compressibility’’ effect which prevents the instability onset. The connection with the magnetohydrodynamic energy principle for stability is demonstrated. A general formalism is developed for any magnetic configuration and applied to a parabolic and a magnetic island topology. Some conclusions concerning the nonlinear tearing mode behavior (explosive phase) are drawn.