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We analyze a suite of global magnetohydrodynamic (MHD) accretion disksimulations in order to determine whether scaling laws for turbulence driven bythe magnetorotational instability, discovered via local shearing box studies,are globally robust. The simulations model geometrically-thin disks with zeronet magnetic flux and no explicit resistivity or viscosity. We show that thelocal Maxwell stress is correlated with the self-generated local verticalmagnetic field in a manner that is similar to that found in local simulations.Moreover, local patches of vertical field are strong enough to stimulate andcontrol the strength of angular momentum transport across much of the disk. Wedemonstrate the importance of magnetic linkages (through the low-densitycorona) between different regions of the disk in determining the local field,and suggest a new convergence requirement for global simulations -- thevertical extent of the corona must be fully captured and resolved. Finally, weexamine the temporal convergence of the average stress, and show that aninitial long-term secular drift in the local flux-stress relation dies away ona time scale that is consistent with turbulent mixing of the initial magneticfield.

Connections Between Local and Global Turbulence in Accretion Disks