Electromagnetic instabilities in rotating magnetized viscous objects

TL;DR

This paper investigates electromagnetic streaming instabilities in rotating, magnetized, viscous astrophysical plasmas, revealing new instability mechanisms influenced by species velocities, viscosity, and thermal effects in various interstellar environments.

Contribution

It derives general expressions for perturbed velocities considering viscosity and thermal pressure, and identifies new instabilities caused by differential velocities of charged species.

Findings

Discovered new compressible instabilities due to species velocity differences.

Derived dispersion relations for axisymmetric perturbations in viscous plasmas.

Showed viscosity effects vary with species and perturbation wavelength.

Abstract

We study electromagnetic streaming instabilities in thermal viscous regions of rotating astrophysical objects, such as, magnetized accretion disks, molecular clouds, their cores, and elephant trunks. The obtained results can also be applied to any regions of interstellar medium, where different equilibrium velocities between charged species can arise. We consider a weakly ionized multicomponent plasma consisting of neutrals and magnetized electrons, ions, and dust grains. The effect of perturbation of collisional frequencies due to density perturbations of species is taken into account. We obtain general expressions for perturbed velocities of species involving the thermal pressure and viscosity in the case in which perturbations propagate perpendicular to the background magnetic field. The dispersion relation is derived and investigated for axisymmetric perturbations. New compressible instabilities generated due to different equilibrium velocities of different charged species are found in the cold and thermal limits when the viscosity of neutrals can be neglected or is important. The viscosity of magnetized charged species is negligible for considered perturbations having wavelengths much larger than the Larmor radius of species. At the same time, the neutrals are shown to be immobile in electromagnetic perturbations when their viscosity is sufficiently large.