Kelvin-Helmholtz Instability at the interface of a disc-corona system

TL;DR

This paper investigates Kelvin-Helmholtz instability at the interface of a thin accretion disc and a hot corona using linear perturbation analysis, revealing potential impacts on disc dynamics and mass-energy exchange.

Contribution

It provides a detailed linear analysis of KH instability at the disc-corona interface, highlighting conditions under which it can influence accretion disc evolution.

Findings

KH instability growth rates are significant within certain parameter ranges.

KH instability can develop on dynamical timescales comparable to the disc's orbital period.

The instability may facilitate mass, angular momentum, and energy exchange between disc and corona.

Abstract

We study Kelvin-Helmholtz (KH) instability at the interface of a disc and corona system by doing a linear perturbation analysis. The disc is assumed to be thin, however, the corona is considered to be nearly quasispherical because of its high temperature. Under these circumstances, the interface is subject to the KH instability for a given set of the input parameters. Growth rates of the KH unstable modes are calculated for a wide range of the input parameters. We show that for a certain range of the perturbations, the unstable KH perturbations are growing with time scales comparable to the inverse of the angular velocity of the accretion disc (dynamical time scale). Thus, KH instability at the interface of a disc-corona may have enough time to affect the dynamical structure of its underlying accretion disc by possible exchange of the mass, angular momentum or even energy. Our linear analysis shows that KH instability may provide a mechanism for such exchanges between a disc and its corona.