Collisionless Kinetic Theory of Oblique Tearing Instabilities

Abstract

The linear dispersion relation for collisionless kinetic tearing instabilities is calculated for a Harris equilibrium. In contrast to the conventional 2D geometry, which considers only modes at the center of the current sheet, modes can span the current sheet in 3D. Modes at each resonant surface have a unique angle ($\theta$) with respect to the guide field direction. Both kinetic simulations and numerical eigenmode solutions of the linearized Vlasov-Maxwell equations have recently revealed that standard analytic theories vastly overestimate the growth rate of oblique modes ($\theta \ne 0$). We find that this stabilization is associated with the density-gradient-driven diamagnetic drift. The analytic theories miss this drift stabilization because the inner tearing layer broadens at oblique angles sufficiently far that the assumption of scale separation between the inner and outer regions of boundary-layer theory breaks down. The dispersion relation obtained by numerically solving a single second order differential equation is found to approximately capture the drift stabilization predicted by solutions of the full integro-differential eigenvalue problem. A simple analytic estimate for the stability criterion is provided.

16 pages, 13 figures, submitted to Physics of Plasmas

References in corpus (6)

• Instability of current sheets and formation of plasmoid chains
• Iris si iv line profiles: An indication for the plasmoid instability during small-scale magnetic reconnection on the sun
• On the Distribution of Plasmoids In High-Lundquist-Number Magnetic Reconnection
• Onset of Fast Reconnection in Hall Magnetohydrodynamics Mediated by the Plasmoid Instability
• Visco-Resistive Plasmoid Instability
• A Two-Fluid Study of Oblique Tearing Modes in a Force-Free Current Sheet

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• Influence of 3D plasmoid dynamics on the transition from collisional to kinetic reconnection
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