Neoclassical dielectric property of a tokamak plasma

The response of a tokamak plasma to a time-dependent axisymmetric radial electric field is considered. The bounce-averaged motion of magnetically trapped ions is shown to consist of a radial drift, in addition to the well-known toroidal precession. This is a neoclassical polarization drift, which is larger than the standard one by a factor B2/B2θ, the square of the ratio of total to poloidal magnetic fields. The resulting low-frequency dielectric constant is larger than the standard one by approximately the same factor, when the ions are in the banana regime of neoclassical theory.