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