Magnetic Reconnection in Accretion Disks

R. Matsumoto (Chiba Univ.) and M. Machida

Magnetic reconnection in accretion disks can be the origin of 
flare-like activities observed in black hole candidates.
We present the results of global three-dimensional magnetohydrodynamic 
simulations of black hole accretion disks. In these simulations,
we explicitly included resistive terms in basic equations. We found 
that accretion of dense blobs creates bisymmetric spiral magnetic 
fields and large-scale current sheets in the innermost plunging region 
of the disk. Magnetic reconnection taking place in the current sheet
releases the accumulated magnetic energy. Numerical results successfully 
reproduced various properties of large-amplitude sporadic X-ray flares 
in black hole candidates known as X-ray shots. Smaller scale magnetic
reconnection in optically thin, turbulent accretion disks can explain 
1/f-like X-ray time variabilities.