Multifaceted Accretion: The Interplay of Turbulence, Resistivity, Thermal Transport, and Dust around Black Holes

Abstract

Accretion near black holes (BHs) is multidimensional, with turbulence, resistivity, thermal transport, and dust dynamics all playing essential roles. In cold accretion discs (ADs) or the region of an AD where magnetic fields (MFs) are negligible (or absent), hydrodynamic (HD) turbulence is probably dominating. However, Magneto-rotational instability (MRI) is the primary cause of turbulence in ADs. Significant velocity variations and rapid pressure changes are characteristics of turbulent flows, which allow better mixing and more angular momentum (AM) and energy transfer. Also, in accretion flow (AF), the interaction between turbulence and resistivity determines the efficiency of energy dissipation and heat transfer. Radiation, convection, and thermal conduction (TC) are the heat transport modes existing in AFs, where TC enables energy transfer in accreting materials via heat flux. Moreover, convection, also generated by turbulence, significantly impacts the stability of the AD and its vertical structure. The disc may be affected by radiation from the AD surrounding the BH when X-ray emission occurs. The emission from the disc is also affected by dust particles. Dust grains near BH are exposed to high temperatures and intense radiation, which might affect the flow characteristics, as seen in Active Galactic Nuclei (AGN). This chapter highlights the combined effect of turbulence, resistivity, transport mechanisms, and dust particles on BH AF. Future studies in this field must thoroughly investigate how dust, transport mechanisms, and turbulence interact in the BH accretion system.