Electromagnetic streaming instabilities of magnetized accretion disks with strong collisional coupling of species

TL;DR

This paper investigates electromagnetic streaming instabilities in magnetized accretion disks with strong collisional coupling, revealing conditions for rapid growth rates that can surpass the Keplerian frequency.

Contribution

It provides a detailed analysis of instabilities considering collisional effects, deriving a dispersion relation and identifying conditions for fast-growing electromagnetic perturbations.

Findings

Dust grains participate in fast electromagnetic perturbations.

Growth rates of instabilities can exceed the Keplerian frequency.

Radial velocities of neutrals and dust grains are inward directed.

Abstract

Electromagnetic streaming instabilities of multicomponent collisional magnetized accretion disks are studied. Sufficiently ionized regions of the disk are explored where there is strong collisional coupling of neutral atoms with both ions and dust grains simultaneously. The steady state is investigated in detail and the azimuthal and radial background velocities of species are calculated. The azimuthal velocity of ions, dust grains, and neutrals is found to be less than the Keplerian velocity. The radial velocity of neutrals and dust grains is shown to be directed inward of the disk. The general solution for the perturbed velocities of species taking into account collisions and thermal pressure is obtained. The effect on the collisional frequencies, due to density perturbations of charged species and neutrals, is included. It is shown that dust grains can be involved in the fast electromagnetic perturbations induced by the ions and electrons through the strong collisions of these grains with neutrals that in turn have a strong collisional coupling with the ions. The dispersion relation for the vertical perturbations is derived and its unstable solutions due to different background velocities of ions and electrons are found. The growth rates of the streaming instabilities considered can be much larger than the Keplerian frequency.