Analytical and numerical treatment of resistive drift instability in a plasma slab
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AVES AND INSTABILITIES IN PLASMA
Analytical and Numerical Treatment of Resistive Drift Instability in a Plasma Slab1 V. V. Mirnov, J. P. Sauppe, C. C. Hegna, and C. R. Sovinec University of Wisconsin-Madison and the Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, Madison, WI, USA e-mail: [email protected] Received October 22, 2015
Abstract—An analytic approach combining the effect of equilibrium diamagnetic flows and the finite ionsound gyroradius associated with electron−ion decoupling and kinetic Alfvén wave dispersion is derived to study resistive drift instabilities in a plasma slab. Linear numerical computations using the NIMROD code are performed with cold ions and hot electrons in a plasma slab with a doubly periodic box bounded by two perfectly conducting walls. A linearly unstable resistive drift mode is observed in computations with a growth rate that is consistent with the analytic dispersion relation. The resistive drift mode is expected to be suppressed by magnetic shear in unbounded domains, but the mode is observed in numerical computations with and without magnetic shear. In the slab model, the finite slab thickness and the perfectly conducting boundary conditions are likely to account for the lack of suppression. DOI: 10.1134/S1063780X16050123
1. INTRODUCTION Numerical modeling of two-fluid current-driven tearing modes in the presence of a pressure gradient [1] have revealed a fluctuation that is destabilized by diamagnetic effects even in the absence of magnetic shear. Linear computations using the NIMROD code are performed for plasma slab with cold ions and hot electrons in a doubly periodic box bounded by two perfectly conducting walls. Within this computational model, configurations with magnetic shear were shown to be unstable to current-driven drift-tearing instability. Our work was originally motivated by a desire to understand the behavior of the drift-tearing mode as it transitions from the collisional to semi-collisional regimes. Previous authors [2, 3] studied this in a periodic domain, and we sought to understand the transition in a bounded domain with perfectly conducting walls, while also including the effects of finite electron thermal conduction. In addition to the drifttearing mode, when performing these simulations we observe another linearly unstable mode driven by the pressure gradient, which we identify as a resistive drift mode. The resistive drift instability, also known as the dissipative drift instability, was originally described in the potential approximation by S.S. Moiseev and R.Z. Sagdeev in [4]. A comprehensive electromagnetic theory of this instability was presented by A.B. Mikhailovskii in his fundamental work [5]. In 1 The article is published in the original.
that paper, he performed a self-consistent analysis of the electron temperature perturbations and derived an elegant condition for validity of the electrostatic approximation. The electromagnetic fluid model was later extended by Mikhailovskii to kinetic calculations with the
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