Speaker
Description
We study a global, two-dimensional (2D) general relativistic magnetohydrodynamics (GRMHD) simulation of an accreting torus around a non-rotating black hole. Our initial configuration is threaded with a net-vertical magnetic flux. This study investigates the effects of initial field strength onto the disk dynamics. We find that the initial net vertical magnetic field significantly enhances its amplification over a few dynamical time scales. The behavior of MRI turbulence is regulated by the initial plasma-$\beta$ (i.e., ratio of gas-to-magnetic pressure) at the inner edge of the torus. Therefore, we perform simulations with different $\beta$ spanning from weakly-to-strongly magnetized cases, $\beta^{\rm in}_{\rm edge} = 2800, 700, 350$, respectively. The shear flow amplifies a strong toroidal magnetic field within the torus via the dynamo process. Consequently, the magnetic fields are sufficient to provide magnetic pressure support for the elevated accretion, $z/R \sim 0.2$. Furthermore, we identify two more regions, (1) gas-pressure dominated dense mid-plane, and (2) moderately magnetized low dense polar region. Finally, over the duration of our simulations, we find an evidence that the net-flux attains a quasi-steady state and can stably maintain an inner disk with surface accretion.
| m.samik@iitg.ac.in | |
| Affiliation | Indian Institute of Technology Guwahati |
