Anomalous Diffusion in Axisymmetric Toroidal Systems

Abstract

We consider the anomalous diffusion in an axisymmetric toroidal plasma due to low-frequency instabilities. The radial, cross-field diffusion is mainly due to the nonconservation of the azimuthal canonical angular momentum. In particular, the electric field component along the magnetic line of force could contribute significantly to the cross-field diffusion by driving a change of the canonical angular momentum. For trapped particles, this diffusion could be ${\left(\frac{B_T}{B_p}\right)}^2$ larger than the $\overrightarrow{\mathrm{E}}\times \overrightarrow{\mathrm{B}}$ diffusion for comparable $E_{\parallel }$ and $E_{\perp }$, where $B_T$ and $B_p$ are the toroidal and poloidal magnetic fields, repectively.