UC San Diego
A closer look at turbulence spreading: How bistability admits intermittent, propagating turbulence fronts
- Author(s): Heinonen, RA
- Diamond, PH
- et al.
Published Web Locationhttps://doi.org/10.1063/1.5138129
In magnetic fusion plasmas, the observation of hysteresis in the turbu- lence intensity level  strongly suggests bistability. Commonly employed reduced models for turbulence spreading are unistable. In this work, a minimal phenomenological model for bistable turbulence spreading is introduced and analyzed. The model is related to the FitzHugh-Nagumo system. In addition to to being able to account for hysteresis, we show that, in contrast to previous models of turbulence spreading, this model predicts stronger penetration of turbulence into the stable core as well as the existence of avalanche-like, intermittent turbulence pulses. We also derive a novel spatial size threshold for the spreading of a localized slug of turbulence. This lays a groundwork for future models, which should include couplings to zonal ow and pro les. This material is based upon work supported by the U.S. Department of Energy, O ffice of Science, Offi ce of Fusion Energy Sciences under Award Number DE-FG02-04ER54738. References  S. Inagaki et al. Nucl. Fusion 53(11):113006 (2013) http://meetings.aps.org/Meeting/DPP18/Session/NP11.73