  Following earlier work, reference is made to the classical entropic force
which results from spatially variable disorder, an exclusively repulsive force.
In terms of macroscopic variables it is applied to magnetohydrodynamics,
causing minor changes on the dispersion of magnetohydrodynamic waves. More
important is its effect in magnetohydrodynamic turbulence. Here the entropic
force affects the ion inertial-range scales on the electron-dominated
perpendicular spectrum causing a steeper than Kolmogorov $\kappa_\perp=-8/3$
spectral slope in agreement with gyro-kinetic simulations. In kinetic theory,
inclusion of the ensemble-averaged entropic force weakly modifies the Langmuir
wave dispersion. It leads to re-formulation of kinetic theory in terms of
Gibbs-Boltzmann-entropy. Liouville's equation in this case becomes an
entropy-kinetic equation under Hamiltonian action, with the entropic
force-density appearing as an additional force term. This entropy-kinetic
equation governs the self-consistent kinetic evolution of the classical entropy
including self-modulation.
