Analogy between mass MD and entropy SD defects, and their equivalent to an energy level (per c2 and temperature, respectively) change during the composition of a system. (a) The mass defect MD constitutes the missing mass between the mass of a composite particle system and the sum of the masses of its constituents A and B; it is caused by the release of the binding energy (mass). (b) The entropy defect SD constitutes the missing entropy between the entropy of a composite particle system and the sum of the entropies of its constituents A and B; it is caused by the order induced by the existence of particle correlations and represents the release of a “binding entropy”.
The recently developed concept of "entropic defect" is important for understanding the foundations of thermodynamics in space plasma physics, and more generally for systems with physical correlations among their particles. Using this concept, this paper derives the basic formulation of the distribution function of velocities (or kinetic energies) in space plasma particle populations. Earlier analyses have shown how the formulation of kappa distributions is interwoven with the presence of correlations among the particles' velocities. This paper shows, for the first time, that the reverse is true: the thermodynamics of particles' physical correlations are consistent only with the existence of kappa distributions.