Magnetohydrodynamic Simulations of Magnetic 
Reconnection in Accretion Disks

S. Numazawa (Chiba Univ.) and R. Matsumoto

We present the results of resistive MHD simulations of differentially 
rotating plasma initially threaded by weak horizontal magnetic fields. 
Gravitational field is assumed to be given by a point source at the 
center. When we assume anomalous resistivity, the system approaches to 
a self-organized critical state, in which differential rotation 
amplifies magnetic fields, meanwhile magnetic energy is sporadically
released by magnetic reconnection. The driving force which sustains
this critical state is the gravity of the central object. When 
resistivity is uniform, after initial amplification, magnetic energy 
gradually decreases by magnetic diffusion.