Time-dependent probability density functions and information diagnostics in forward and backward processes in a stochastic prey–predator model of fusion plasmas

摘要: Forward and backward processes associated with the low-to-high (L-H) transition in magnetically confined fusion plasmas are investigated by using a time-dependent probability density function (PDF) approach information length diagnostics. Our model is based on extension of deterministic prey–predator-type [Kim Diamond, Phys. Rev. Lett. 90, 185006 (2003)] to stochastic including two independent, short-correlated Gaussian noises. The “forward” process consists ramping up input power linearly time so that zonal flows self-regulate turbulence after their initial growth from turbulence. “backward” ramps down again, starting at t = * when switched Q ( ) 2 − for > *, decreasing until *. Using three choices Q(t), differing rates, PDFs calculated numerically solving appropriate Fokker–Planck equation, several statistical measures forward investigated. lengths L x v flows, respectively, path-dependent dimensionless numbers, representing total number statistically different states evolve through t. In particular, shown be strongly non-Gaussian convoluted structures multiple peaks, intermittency playing key role regulation. stark difference between captured corresponding latter give us useful insight into understanding correlation self-regulation, self-regulatory dithering phase.