We formulate the problem of confined Lévy flight on a comb. The comb represents a sawtoothlike potential field $V\left(x\right)$, with the asymmetric teeth favoring net transport in a preferred direction. The shape effect is modeled as a power-law dependence $V\left(x\right)\propto {\left|\mathrm{\Delta }x\right|}^n$ within the sawtooth period, followed by an abrupt drop-off to zero, after which the initial power-law dependence is reset. It is found that the Lévy flights will be confined in the sense of generalized central limit theorem if (i) the spacing between the teeth is sufficiently broad, and (ii) $n>4-\mu$, where $\mu$ is the fractal dimension of the flights. In particular, for the Cauchy flights ($\mu =1$), $n>3$. The study is motivated by recent observations of localization-delocalization of transport avalanches in banded flows in the Tore Supra tokamak and is intended to devise a theory basis to explain the observed phenomenology.

• Received 20 April 2018
• Revised 19 June 2018

DOI:https://doi.org/10.1103/PhysRevE.98.022208