The Evolution of Channel Flows in MHD Turbulence Driven by Magnetorotational Instability

MHD turbulence driven by magnetorotational instability (MRI) in accretion disks is investigated using the local shearing box calculations. The growth of many short-wavelength MRI modes, which are called “channel flows”, is found in the spatial distribution of the current density. These small channel flows can be regarded as a unit structure of MRI driven turbulence. Nonlinear evolution of the channel flow affects the saturation amplitude and time variability of the Maxwell stress. Exponential growth of a channel mode is stopped by the Kelvin-Helmholtz type instability which triggers the subsequent magnetic reconnection. The characteristics of the magnetic reconnection are consistent with the Sweet-Parker model. These studies of the nonlinear evolution of the channel flow are required to understand the saturation mechanism of the MRI.