Temperatures in grains and plasma

Theoretische Physik, Universität Tübingen - 72076 Tübingen, Germany, EC

^(a) mliu@uni-tuebingen.de (corresponding author)

Received: 21 May 2021
Accepted: 9 August 2021

Abstract

Grains are widely assumed to be characterized by a single temperature —derived either from the configurational entropy, or employing the kinetic theory. Yet granular media do have two temperatures, T_g and T, pertaining to the grains and atoms. It is argued here that a two-temperature plasma yields a more useful analogy for grains than a molecular gas: 1) Irreversible collisions also occur in plasma, to reach the equilibrium of equal temperature. 2) The plasma energy is not linear in the two temperatures; it is quadratic in the temperature difference, minimal at equilibrium. Both points have valid analogues in grains, yielding useful insights.