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Lower-hybrid drift and Buneman instabilities operate in current sheets with or without the guide field. The lower-hybrid drift instability is a universal instability in that it operates for all parameters. In contrast, the excitation of Buneman instability requires sufficiently thin current sheet. That is, the relative electron-ion drift speed must exceed the threshold in order for Buneman instability to operate. Traditionally, the two instabilities were treated separately with different mathematical formalisms. In a recent paper, an improved electrostatic dispersion relation was derived that is valid for both unstable modes [P. H. Yoon and A. T. Y. Lui, Phys. Plasmas 15, 072101 (2008)]. However, the actual numerical analysis was restricted to a one-dimensional situation. The present paper generalizes the previous analysis and investigates the two-dimensional nature of both instabilities. It is found that the lower-hybrid drift instability is a flute mode satisfying k·B=0 and k·∇n=0, where k represents the wave number for the most unstable mode, B stands for the total local magnetic field, and ∇n is the density gradient. This finding is not totally unexpected. However, a somewhat surprising finding is that the Buneman instability is a field-aligned mode characterized by k×B=0 and k·∇n=0, rather than being a beam-aligned instability. [ABSTRACT FROM AUTHOR]

The Rayleigh-Taylor instability arises whenever two fluids with different densities are arranged such that the heavier fluid sits above the lighter fluid, with a sharp interface in between. The magnetic Rayleigh-Taylor instability has the further complication due to the presence of a magnetic field throughout both media. The two fluids in question may also have differing magnetic properties, such as the magnetic permeability. When the fluids in consideration are in fact plasmas comprised of charged particles, induced currents, magnetic fields, and Lorentz forces can all act in ways that will affect the stability of the system. Stable base flows exist for the 2D case, and small sinusoidal disturbances to the base flow will grow in the unstable scenario. The numerical method described in this paper calculates the growth of the interface in the nonlinear regime, since closed form solutions are obtained only in the linear approximation. Through the analysis of both the fluid and magnetic vorticities and streamfunctions, the simulated results can be explained from the principles of magnetohydrodynamics. A range of simulations is presented, looking at cases with different initial conditions, cases with strong and weak magnetic fields, and cases with magnetic fields oriented at different angles relative to the interface of the two fluids. It is shown in particular how different initial conditions give rise to outcomes that are very different in terms of the geometry of the interface between the two fluids, primarily the differences between a single mode disturbance and a multimode disturbance to the interface at time t = 0. [ABSTRACT FROM AUTHOR]

In a magnetized plasma with a temperature anisotropy T||>T⊥ (where || and ⊥ denote directions with respect to the uniform magnetic field B0), the nonresonant Weibel instability can develop and destabilize purely growing, ordinary plasma modes (k=k⊥). This paper presents a rigorous extended analysis of this instability on the basis of a new threshold b0(k), which enables to determine the instability conditions as well as the upper limits of the growth rates. Accurate analytical forms of the threshold conditions are provided here for the first time and for the full physical range of the temperature anisotropy and the parallel plasma beta. The marginal and threshold conditions for the plasma parameters, which directly lead to an instability of the ordinary mode, are explicitly derived numerically and analytically. The new analytical tools developed here provide premises for a comprehensive investigation of the interplay of this instability with the firehose instability, as they both can develop in the same conditions. [ABSTRACT FROM AUTHOR]

Nonlinear dynamic evolution of the double tearing mode (DTM) with a guiding magnetic field (By0) is investigated by magnetohydrodynamical numerical simulation. The dynamic process of DTM depends weakly on the guiding field in the weak guiding field regime (By0≤1), but is suppressed by a strong guiding field (By0>2). During the explosive nonlinear phase, the maximum reconnection rate (γmax) increases weakly with the increase of the resistivity as γmax~η0.06 for By0≤1, but for By0>2, γmax is nearly independent of the resistivity. The maximum reconnection rate in the explosive growth phase increases with increase of the initial current sheet separation. A secondary tearing instability is observed at moderate current sheet separation. A strong guiding field suppresses the formation of a secondary island. Based on the simulation results, it is found that the secondary tearing instability occurs only when the length-to-thickness aspect ratio of the reconnection region exceeds about 20. [ABSTRACT FROM AUTHOR]

It is found that the zero-order current associated with electron shear flow produces a drift wave in magnetized plasmas, which can become unstable under certain conditions. This wave will be particularly important in low density and low temperature plasmas of heavy ions. As an example, numerical estimates are presented for a barium plasma with parameters compatible with experiments. [ABSTRACT FROM AUTHOR]