Particle heating in advection-dominated accretion flows (ADAFs) by nonlinear MHD (Alfvénic) turbulence is investigated. Such turbulence with highly-fluctuating magnetic fields, B̃ ∼ B0, is believed to be naturally produced by the magnetic shearing instability near the nonlinear saturation. It is shown that the energy is dissipated in the parallel cascade, which occurs due to nonlinear compressib...

We calculate the structure of accretion disc around a rapidly rotating black hole with a super-Eddington accretion rate. The luminosity and height of the disc are reduced by the advection effect. In the case of a large viscosity parameter, α > 0.03, the accretion flow strongly deviates from thermodynamic equilibrium and overheats in the central region. With increasing accretion rate, the flow t...