Time variabilities of optically thin black hole accretion disks reproduced by 3D MHD simulations

We analysed the results of long time-scale global three-dimensional resistive magneto-hydrodynamic simulations of radiatively inefficient accretion flows onto a black hole. We found that the power spectral density (PSD) of the time variation of the mass accretion rate has a power law dependence f ^-a with index a ∼ 1.5 in the frequency range 1M₁₀ ^-1Hz < f < 80M₁₀ ^-1 Hz, where M ₁₀ = M/10M⊙ is the mass of the black hole. The PSD has a high frequency break at f ∼ 80M₁₀ ^-1Hz, above which a ∼ 2.4, and another break in the lower frequency range at f ∼ 1M ₁₀ ^-1Hz. Numerical results indicate that the high frequency break is related to disk oscillation in the innermost region of the disk. The lower frequency break of the PSD is due to the quasi-periodic mass accretion from the outer region.