Turbulence and Magnetic Reconnection for Large Magnetic Prandtl Numbers
Abstract
We have studied the small scale turbulent cascade in the limit of high magnetic Prandtl numbers. When viscosity is much larger than resistivity, as expected in hot low density environments, the usual turbulent cascade will terminate at the viscous damping scale. Below this the magnetic fields will respond to stresses created by larger scale eddies, but motions are strongly suppressed. We present numerical studies of the relative ratio of viscous to resistive damping and show that they are consistent with strong intermittency in the perturbed magnetic field. The magnetic field creates domains approximately the size of the viscously damped eddies, with relatively uniform fields inside each domain. The domain boundaries have a finite thickness which scales with the square root of the resistivity. Within each domain trajectories along magnetic field lines will diverge exponentially. However, in the domain boundaries adjacent trajectories will spread much more rapidly. Consequently, reconnection between adjacent domains occurs in a viscous eddy turnover time, and is insensitive to the value of the resistivity. The slope of the magnetic power spectrum below the viscous damping scale has an extra degree of freedom, depending on the anisotropy of the magnetic field in the domain walls. We illustrate this by comparing results for different large scale conditions.
- Publication:
-
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23333407V