A poloidally varying electrostatic potential due to the toroidal drift and heat flux across a flux surface generated by this potential are investigated for a multi-species plasma in tokamaks. By determining this electrostatic potential self-consistently using quasi-neutrality, the heat flux is calculated in the banana, plateau and collisional regimes. Using the results in these asymptotic regimes, a continuously valid expression throughout all collisionality regimes is presented. The electron heat flux is found to exceed the conventional one in the absence of the poloidally varying potential by a factor square root mi/me in all collisionality regimes, where me and mi are the masses of the electron and the ion. The numerical factor for the continuously valid expression is explicitly computed for a simple plasma in a tokamak with circular cross section. An analytic form for the heat flux in a weakly modulated magnetic field is also discussed.
Magnetic flux coordinates for analytic high-beta tokamak equilibria with flow