Response to “Comment on ‘Paleoclassical transport in low-collisionality toroidal plasmas’ ” [Phys. Plasmas 14, 104701 (2007)]

The Comment mainly poses questions related to the validity and applicability of the key hypothesis of the paleoclassical model of radial electron heat transport, which is that electron guiding centers diffuse radially along with thin annuli of poloidal magnetic flux in resistive, current-carrying axisymmetric toroidal plasmas. While this key hypothesis was only motivated phenomenologically in the original toroidal paper, a derivation of it has recently been published. The derivation is based on transforming the drift-kinetic equation from laboratory to poloidal magnetic flux coordinates in a situation where the poloidal flux obeys a diffusion equation. Since the derivation in Ref. 3 was carried out in the full axisymmetric toroidal magnetic field geometry and is somewhat complicated, it is helpful to present and discuss a simpler model that illustrates the key points involved. These key points are crucial for addressing the main issues raised in the Comment. Thus, consider the general procedure for solving a simple one-dimensional plasma kinetic equation, which is a first order partial differential equation PDE for f x , t in the two variables x , t,