Mean Field Dynamo in Thick Disks around Kerr Black Holes: High Order Axisymmetric Simulations

We present here a kinematic study of dynamo effects in thick accretion disks using the most recent version of the ECHO code. This allowed us to perform high-order simulations of a resistive plasma within the 3 + 1 GRMHD frame with a fully covariant mean-field dynamo closure for the Ohm's law. The magnetic field goes through an exponential growth within few orbital periods of the disk, and we derive butterfly diagrams qualitatively in the same fashion as in the Sun. Finally, a typical time-scale of the field evolution is found, that depends on the dynamo and resistivity parameters and that could be related to the periodicities observed in several accreting systems.