Abstract
We solve the linearised Vlasov-Fokker-Planck (VFP) equation to show that heat flow or an electrical current in a magnetized collisional plasma is unstable to the growth of a circularly polarised transverse perturbation to a zeroth order uniform magnetic field. The Braginskii [1965 Rev Plasma Phys 1 205] transport equations exhibit the same instability in the appropriate limit. This is relevant to laser-produced plasmas, inertial fusion energy (IFE) and to dense cold interstellar plasmas.
Highlights
In plasmas, particle momentum distributions are rarely Maxwellian and isotropic
We find that magneto-collisional instabilities are present (i) in relatively relaxed plasmas in which the energy flux is carried by electrons in the high velocity tail of a Maxwellian distribution and (ii) in plasmas far from equilibrium in which an independent population of high velocity charged particles, such as cosmic rays or laser-produced energetic protons or electrons, pass through a thermal plasma
We have solved the linearised electron VFP equations coupled to the Maxwell equations and the cold ion equation of motion for a magnetised collisional plasma
Summary
Particle momentum distributions are rarely Maxwellian and isotropic. They frequently carry a large energy flux or a component of energetic particles. The magnetocollisional instability may be relevant in low density weakly collisionless plasmas where the growth time is of the order of the collision time which, despite being long compared to the Larmor gyration time, may be short compared to the timescale for hydrodynamic evolution. Since both collisions and Larmor gyration are important, the derivation of the general dispersion relation requires solution of the Vlasov-Fokker-Planck (VFP) equation in which advection, collisions, the effect of magnetic and electric field, and high order anisotropies are modelled. We find that the Braginskii and VFP growth rates are mutually consistent within Braginskii’s scheme of approximation
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