The Magnetoviscous-thermal Instability
  Accretion flows onto underluminous black holes, such as Sagittarius A* at the
center of our galaxy, are dilute (mildly collisional to highly collisionless),
optically thin, and radiatively inefficient. Therefore, the accretion
properties of such dilute flows are expected to be modified by their large
viscosities and thermal conductivities. Second, turbulence within these systems
needs to transport angular momentum as well as thermal energy generated through
gravitational infall outwards in order to allow accretion to occur. This is in
contrast to classical accretion flows, in which the energy generated through
accretion down a gravitational well is locally radiated. In this paper, using
an incompressible fluid treatment of an ionized gas, we expand on previous
research by considering the stability properties of a magnetized rotating
plasma wherein the thermal conductivity and viscosity are not negligible and
may be dynamically important. We find a class of MHD instabilities that can
transport angular momentum and thermal energy outwards. They are plausible
candidates to describe accretion in radiatively inefficient accretion flows
(RIAFs). We finish by discussing the implications for analytic models and
numerical MHD simulations of mildly dilute or collisionless astrophysical
plasmas, and immediate directions for further research.
