Reconnection in a weakly stochastic field

We examine the effect of weak, small-scale magnetic held structure on the r ate of reconnection in a strongly magnetized plasma. This affects the rate of reconnection by reducing the transverse scale for reconnection hows and by allowing many independent flux reconnection events to occur simultaneous ly. Allowing only for the first effect and using Goldreich & Sridhar's mode l of strong turbulence in a magnetized plasma with negligible intermittency , we find a lower limit for the reconnection speed similar to (VARL-3/16M3/ 4),where V-A is the Alfven speed, R-L is the Lundquist number, and M is the large-scale magnetic Mach number of the turbulence. We derive an upper Lim it of similar to VAM2 by invoking both effects. We argue that generic recon nection in turbulent: plasmas will normally occur at close to this upper li mit. The fraction of magnetic energy that goes directly into electron heati ng scales as (RL-2/5M8/5), and the thickness of the current sheet scales as RL-3/5M-2/5. A significant fraction of the magnetic energy goes into high- frequency Alfven waves. The angle between adjacent held lines on the same s ide of the reconnection layer is similar to (RL-1/5M6/5) on the scale of th e current sheet thickness. We claim that the qualitative sense of these con clusions, that reconnection is fast even though current sheets are narrow, is almost independent of the local physics of reconnection and the nature o f the turbulent cascade. As the consequence of this the Galactic and solar dynamos are generically fast, i.e., do not depend on the plasma resistivity .