Speaker
Description
We present the results of three-dimensional global radiation magnetohydrodynamic simulations of state transitions in black hole candidates. During the hard-to-soft state transition, accretion flow near the black hole tends to be in optically thin hot state even when the accretion rate exceeds the upper limit for RIAF in the outer region. In such state, RIAF near the black hole co-exists with the outer radiatively cooled disk. We found that the temperature of the radiatively cooled disk is higher than the standard disk because the magnetic energy enhanced around the interface between RIAF and the cooled disk is transported radially outward around the equatorial region and heats the disk by releasing the magnetic energy through magnetic reconnection. This non-local heating keeps the disk temperature around 10KeV in stellar mass black holes and 1KeV in super-massive black holes. This mechanism explains the hard X-ray emission in bright hard state and the soft X-ray excess during changing look phenomena in active galactic nuclei,
