GR/MHD SIMULATIONS OF ACCRETION ONTO BLACK HOLES (cont.) Jean-Pierre De Villiers John Hawley Shigenobu Hirose JHK

TOPICS Magnetic Field Distribution and Structure Accretion Fluctuations Angular Momentum Flow and Stress Distribution Connection to Dissipation Possible Consequences for Observations

Magnetic Field Intensity a/M=0 a/M=0.5 a/M=0.9a/M=0.998

Field-line Shapes a/M = 0.9: disk bodya/M = 0.9: corona For more detail, see poster by S. Hirose

Accretion History

Accretion Rate Power Spectrum

Angular Momentum Flow Magnetic torques cause outward angular momentum flow, permit mass inflow Steady-state inflow achieved when angular momentum losses to outward rings match gains from inner Net flow subtracts torques from that associated with rest-mass of matter, its enthalpy, and advected magnetic energy

Angular Momentum Flux Key: = matter, = torque, = Angular momentum at these radii increases over time

Novikov-Thorne Model Geometrically-thin, time-steady disks Conserve rest-mass, energy, angular momentum Guess the conserved angular momentum flux by assuming zero stress inside the marginally stable orbit. Compute stress, dissipation, energy release

Exception! Magnetic Fields E.g., as pointed out in Page & Thorne (1974), Thorne (1974), K. (1999), Gammie (1999), Magnetic fields can stretch across the marginally stable region, exerting large stresses even when connected to matter of little inertia

Fluid Frame Stress

Angular Momentum Flux per Rest-Mass Large outward a.m. flux carried electromagnetically

Two Views of Dissipation Global: difference between orbital energy released in accretion and work done by torques---related to integrated stress Local: resistivity, reconnection, etc.--- related to small-scale magnetic structure

Locations of Dissipation (?) a/M=0 a/M=0.5 a/M=0.9a/M=0.998

Dynamical Implications Limit to spin-up? Larger radiation efficiency? Altered surface density in inner disk, depends on black hole spin Strong fluctuations Are we seeing a Blandford-Znajek analog?

Radiation Implications Greater dissipation overall, particularly in inner disk and plunging region---harder spectra, especially edge-on, more illumination of outer disk by returning radiation Coronal activity concentrated in inner region (?)--- test with Fe K alpha profiles Inner edge of thermal radiation not same as inner edge for reflection not equal to radius of ISCO Fluctuations drive “red noise” in lightcurves (?)