Study of L-->H bifurcation for a simple model of coupled heat and particle fluxes including curvature of the pressure profile

A transport bifurcation model of Hinton and Staebler (Hinton and Staebler, 1993, Ph. Fl. 5, 1281) is solved analytically. While independent evolution equations for density and pressure are obtained, both the particle and heat sources enter each equation. For a simple regularization scheme, an exact criterion for local co-existance of L and H phase is derived. It is also shown that inclusion of the curvature of radial pressure profile results in a different transition criterion than in the case of a linear pressure profile. While in the linear case the transition criterion is determined by the Maxwell equal area rule, in the case of a curved pressure profile the transition occurs at lower heat and particle fluxes.