High-order Schemes for Non-ideal 3+1 GRMHD: A Study of the Kinematic Dynamo Process in Accretion Tori
We present the first astrophysical application of the ECHO code in its recent version supplemented by a generalized Ohm law, namely a kinematic study of dynamo effects in thick accretion disks. High-order implicit-explicit Runge-Kutta time-stepping routines are implemented and validated within 3+1 General Relativistic MagnetoHydroDynamics (GRMHD). The scheme is applied to a differentially rotating torus orbiting a Kerr black hole, where the mean-field dynamo process leads to strong amplification of seed magnetic fields. We show that the interplay between the toroidal and poloidal components occurs qualitatively in the same fashion as in the Sun, butterfly diagrams are reproduced, and a typical time-scale for the field evolution is found, depending on the dynamo and resistivity numbers, which could explain periodicities as observed in several accreting systems.
8th International Conference of Numerical Modeling of Space Plasma Flows (ASTRONUM 2013)
- Pub Date:
- September 2014
- Astrophysics - High Energy Astrophysical Phenomena
- 6 pages, Proceedings of ASTRONUM 2013, Biarritz. To appear as ASP Conference Series