Turbulence and flows in stochastic magnetic fields
Patrick Diamond
University of California San Diego

The theory of shear (especially zonal) flows and their impact on turbulence and transport has been studied intensively. Progress is still ongoing. The goal of reconciling good confinement with satisfactory power handling drives us to revisit this familiar subject (and others) in new contexts. One such problem is the effect of a stochastic magnetic field — as, say, produced by a RMP (Resonant Magnetic Perturbation) — on flow shear and the L à H transition. There, ELM mitigation comes at the price of an increase in the L à H power threshold. Interestingly, the basic physics of this question has many aspects in common with that of momentum transport in the solar tachocline. Both are problems in shear flow formation in a disordered magnetic field.

In this talk, I’ll overiew the basic physics of shear flows in plasmas, and briefly describe two lines of ongoing development. Then I’ll discuss shear flow formation in the tangled, planar magnetic field expected in the solar tachocline. A mean field model of the system as a resisto-elastic medium will be discussed. Finally, I’ll discuss Reynolds stress decoherence due to stochastic magnetic field in tokamaks, and will predict the scaling of the resulting increment in the L à H power threshold.

Research supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, under Award Number DE-FG02-04ER54738. Collaborators include Samantha Chen, Rameswar Singh, Steve Tobias and others.

Join Zoom Meeting
https://mit-psfc.zoom.us/j/6174522043?pwd=NHN3ZHFURUJLM0VkQnprOVkyaVhNUT09

Meeting ID: 617 452 2043
Passcode: Fusion