The Magnetothermal Instability And Its Role In Angular Momentum Transport in Hot, Dilute Magnetized Accretion

Recent observations have demonstrated the prevalence of underluminous accretion flows in massive and supermassive central galactic black holes, for which the best studied example is that of Sagittarius A* at the center of our Milky Way. In addition, circular polarization measurements of millimeter-wavelength radiation from Sagittarius A* has shown the existence of measurable magnetic fields in the source. These flows are characterized by the radiatively inefficient accretion of a hot, mildly collisional to highly collisionless, and optically thin plasma onto a black hole. The energy generated through the accretion of matter down a gravitational well cannot be efficiently radiated and therefore must be advected outwards. We show that the collisionless and mildly collisional MTI, an MHD mode of a dilute rotationally supported plasma, can destabilize these dilute, magnetized, radiatively inefficient flows and can carry out angular momentum and energy in order to allow accretion to occur.