Low-angular-momentum General Relativistic Magnetohydrodynamic Accretion Flows around Rotating Black Holes with Shocks

Abstract

We investigate the global structure of the general relativistic magnetohydrodynamic (GRMHD) accretion flows around Kerr black holes containing shock waves, where the disk is threaded by radial and toroidal magnetic fields. We self-consistently solve the GRMHD equations that govern the flow motion inside the disk and for the first time, to our knowledge, we obtain the shock-induced global GRMHD accretion solutions around weakly as well as rapidly rotating black holes for a set of fundamental flow parameters, such as energy ( ${ \mathcal E }$ ), angular momentum ( ${ \mathcal L }$ ), radial magnetic flux (Φ), and isorotation parameter ( F ). We show that shock properties—namely, the shock radius ( r _sh ), compression ratio ( R ), and shock strength (Ψ)—strongly depend on ${ \mathcal E }$ , ${ \mathcal L }$ , Φ, and F . We observe that the shock in the GRMHD flow continues to exist for a wide range of the flow parameters, which allows us to identify the effective domain of the parameter space in the ${ \mathcal L }\mbox{--}{ \mathcal E }$ plane where shock solutions are feasible. Moreover, we examine the modification of the shock parameter space and find that it shifts towards the lower-angular-momentum values with increasing Φ and black hole spin ( a _k ). Finally, we compute the critical radial magnetic flux (Φ ^cri ) that admits shocks in GRMHD flows and ascertain that Φ ^cri is higher (lower) for a black hole of spin a _k = 0.99 (0.0) and vice versa.

Keywords

• Accretion
• Magnetohydrodynamics
• Black hole physics
• Magnetic fields
• Shocks