Magnetohydrodynamic stability of stochastically driven accretion flows

TL;DR

This paper studies how stochastic noise influences magnetohydrodynamic perturbations in rotating shear flows, revealing that noise can induce instability and turbulence in flows that are linearly stable but astrophysically relevant.

Contribution

It introduces the effect of stochastic noise on magnetohydrodynamic flows, showing how it can lead to instability in Rayleigh stable but astrophysically significant flows.

Findings

Stochastic noise causes large autocorrelations and energy dissipation in perturbations.

Noise-induced effects can explain turbulence in flows stable under linear theory.

Magnetorotational instability is influenced by stochastic perturbations.

Abstract

We investigate the evolution of magnetohydrodynamic perturbations in presence of stochastic noise in rotating shear flows. The particular emphasis is the flows whose angular velocity decreases but specific angular momentum increases with increasing radial coordinate. Such flows, however, are Rayleigh stable, but must be turbulent in order to explain astrophysical observed data and, hence, reveal a mismatch between the linear theory and observations/experiments. The mismatch seems to have been resolved, at least in certain regimes, in presence of weak magnetic field revealing magnetorotational instability. The present work explores the effects of stochastic noise on such magnetohydrodynamic flows, in order to resolve the above mismatch generically for the hot flows. It is found that such stochastically driven flows exhibit large temporal and spatial autocorrelations and cross-correlations of perturbation and hence large energy dissipations of perturbation, which generate instability.