Entropy production determination of the ambipolar solution nearest equilibrium

A general derivation of the entropy production equation is presented for a confined plasma which loses particles and energy via radial transport and, perhaps, end loss. The resulting equation is employed to determine which root or solution at each pressure surface is closest to local thermodynamic equilibrium when more than one self-consistent or ambipolar solution is possible. The solution closest to local thermodynamic equilibrium is by definition the one with the smallest total collisional entropy production rate. This solution makes the distribution functions as close to a local Maxwellian as possible and is conjectured to be the root of physical interest.