2007/05/03 by Siming Liu, Christopher L. Fryer, Chris L. Fryer +4
Engineering · Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics (astro-ph) #FOS: Physical sciences #Heat Transfer Mechanisms #astro-ph
paper · pdf · doi:10.48550/arxiv.0705.0525
25 pages, 2 figures, submitted to ApJ
openalex publication_date 2007/05/03 · arxiv created 2007/07/03 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Plasmas in an accretion flow are heated by MHD turbulence generated through the magneto-rotational instability. The viscous stress driving the accretion is intimately connected to the microscopic processes of turbulence dissipation. We show that, in a few well-observed black hole accretion systems, there is compelling observational evidence of efficient electron heating by turbulence or collective plasma effects in low accretion states, when Coulomb collisions are not efficient enough to establish a thermal equilibrium between electrons and ions at small radii. However, charged particles reach a thermal equilibrium with their kind much faster than with others through Coulomb collisions, a two-temperature accretion flow is expected. We consider a Keplerian accretion flow with a constant mass accretion rate in the pseudo-Newtonian gravitational potential and take into account the bremsstrahlung, synchrotron, and inverse Comptonization cooling processes. The critical mass accretion rate, below which the two-temperature solution may exist, is determined by the cooling processes and the collisional energy exchanges between electrons and ions and has very weak dependence on the collision-less heating of electrons by turbulence, which becomes more important at lower accretion rates. Collision-less heating of electrons by MHD turbulence can no longer be ignored in quantitative investigations of these systems.