An Overview of Rossby Wave Instability in Accretion Discs surrounding Black Holes

Abstract

The Rossby Wave Instability (RWI) has become an important concept in understanding the hydrodynamics (HDs) of accretion discs (ADs), especially in systems around black holes (BHs) where magnetic effects are either weak or absent. This instability is triggered by extrema (or sharp gradients) in the vortensity profile of the disc. Once activated, it leads to non-axisymmetric disturbances that can grow into large-scale vortices. These vortices play a significant role in the outward transport of angular momentum (AM). They may also help explain the presence of quasi-periodic oscillations (QPOs) observed in certain astrophysical systems such as X-ray binaries (XRBs). Here we review the main theoretical ideas behind RWI, as well as findings from more advanced three-dimensional (3D) and relativistic simulations. We also mention how the theory has been extended to include magnetic fields and self-gravity(SG) and what these results might imply for actual observations.