Combined dynamo of gravitational and magneto-rotational instability in irradiated accretion discs

Aims. We aim to assess whether magneto-rotational instability (MRI) can exist in a turbulent state generated by gravitational (GI). investigated the magnetic field saturation and elucidated ability of GI turbulence act as dynamo. Methods. The results were obtained numerical simulations using magnetohydrodynamics code Athena . A sub-routine solve Poisson equation for self-gravity three-dimensional Fourier transforms was implemented that purpose. GI-turbulent then restarted, with zero-net-flux type seed being introduced. chosen β ≈ 10 make sure stationary is exclusively Results. Shortly after introducing field, significant amplification observed, despite MRI not active. This shows acts kinematic growing allows become active, which leads emergence butterfly diagram. stress saturated found be consistent superposition stresses stresses. Moreover, ratio pressure lie 0.3−0.4 range, typical turbulence. Furthermore, it energy significantly decreases if turned off. indicates, accordance initial amplification, provides dominant dynamo contribution simply added but rather grows on provided Finally, shown combined GI-MRI-dynamo an α − Ω model observed oscillation frequency diagram roughly agrees prediction.