Radiatively inefficient accretion flows

In this study, we discuss the physical instability defining the expected turbulence in Radiatively Inefficient Accretion Flows (RIAFs) around the supermassive black holes (e.g., Sagittarius A* in the center of our Galaxy). These flows, with a high probability, include weakly collisional hot, optically thin and dilute plasmas. Within these flows, gravitational potential energy brought about by turbulent stresses is trapped as heat energy. Thus, in order for accretion to be realized, outward transport of heat as well as angular momentum is required. This outward heat transport may reduce the mass inflow rate on black hole. MHD equations including variation of viscosity coefficients with pressure in the momentum conservation equation are solved. A result of the linear instability analysis, the dispersion relation including a fifth degree equation with complex coefficients is derived and the solutions of the dispersion relation are discussed. It is deduced that the instability is independent from signs of the temperature gradient, the gyroviscosity and the rotation profile and also from the value of the plasma beta parameter. It is seen that the instability is so powerful and occurs at all wavenumbers.