Magnetohydrodynamic shocks near rotating black holes
Rilett, Darrell Jon
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The theory of general relativistic magnetohydrodynamic standing shock formation is analyzed for accreting MHD plasma in a rotating, stationary, and axisymmetric black hole magnetosphere. All postshock physical quantities are expressed in terms of the relativistic compression ratio. The compression ratio is a solution of a seventh degree polynomial, incorporating the jump conditions, that is to be solved simultaneously with an equation for the polytropic index of the postshock plasma. Then the downstream state of the shocked plasma is determined entirely in terms of preshock quantities. Slow and fast magnetosonic shock solutions are analyzed for both equatorial and non-equatorial accretion flows. Shock categories for fast and slow shocks are developed, based on conserved quantities. These categories relate the initial conditions of a preshock flow to the spin of the black hole and can be used as a predictor of shock strength and location. We show that shocks may produce a hot region close to the horizon that could be applied to the generation mechanism of the iron fluorescence line from a Seyfert nucleus.