The Properties of Reconnection Current Sheets in GRMHD Simulations of Radiatively Inefficient Accretion Flows

摘要

Non-ideal MHD effects may play a significant role in determining thedynamics, thermal properties, and observational signatures of radiativelyinefficient accretion flows onto black holes. In particular, particleacceleration during magnetic reconnection events may influence black holespectra and flaring properties. We use representative GRMHD simulations ofblack hole accretion flows to identify and explore the structures andproperties of current sheets as potential sites of magnetic reconnection. Inthe case of standard and normal (SANE) disks, we find that, in the reconnectionsites, the plasma beta ranges from $0.1$ to $1000$, the magnetization rangesfrom $10^{-4}$ to $1$, and the guide fields are weak compared to thereconnecting fields. In magnetically arrested (MAD) disks, we find typicalvalues for plasma beta from $10^{-2}$ to $10^3$, magnetizations from $10^{-3}$to $10$, and typically stronger guide fields, with strengths comparable to orgreater than the reconnecting fields. These are critical parameters that governthe electron energy distribution resulting from magnetic reconnection and canbe used in the context of plasma simulations to provide microphysics inputs toglobal simulations. We also find that ample magnetic energy is available in thereconnection regions to power the fluence of bright X-ray flares observed fromthe black hole in the center of the Milky Way.