A Two-Fluid Model for Particle Acceleration and Dynamics in Black-Hole Accretion Flows




Lee, Jason P.

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Hot, tenuous Advection-Dominated Accretion Flows (ADAFs) are ideal sites for the Fermi acceleration of relativistic particles at standing shock waves in the accretion disk. Previous work has demonstrated that the shock-acceleration process can be efficient enough to power the observed, strong outflows in radio-loud active galaxies such as M87. However, the dynamical effect (back-reaction) on the flow, due to the pressure of the relativistic particles, has not been previously considered, as this effect can have a significant influence on the disk structure. We reexamine the problem by creating a new two-fluid model that includes the dynamical effect of the relativistic particle pressure, as well as the background (thermal) gas pressure. The new model is analogous to the incorporation of the cosmic-ray pressure in the two-fluid model of cosmic-ray-modified supernova shock waves. We derive a new set of shock jump conditions and obtain dynamical solutions that describe the structure of the disk, the discontinuous shock, and the outflow. From this, we show that smooth (shock-free) global flows are impossible when relativistic particle diffusion is included in the dynamical model.



Astrophysics, Theoretical physics, Acceleration of particles, Accretion disks, Black hole physics, Hydrodynamics, Jets, Shock waves