Maximum-entropy states for magnetized ion transport

•Ion stratification is identified as a maximum-entropy state.•Entropy maximization replicates known impurity physics under fewer assumptions.•Most details of the collision operator are irrelevant to the resulting equilibria. For a plasma with fixed total energy, number of particles, and momentum, the distribution function that maximizes entropy is a Boltzmann distribution. If, in addition, the rearrangement of charge is constrained, as happens on ion-ion collisional timescales for cross-field multiple-species transport, the maximum-entropy state is instead given by the classic impurity pinch relation. The maximum-entropy derivation, unlike previous approaches, does not rely on the details of the collision operator or the dynamics of the system, only on the presence of certain conservation properties.