A nonthermal plasma, cold plasma or non-equilibrium plasma is a plasma which is not in thermodynamic equilibrium, because the electron temperature is much hotter than the temperature of heavy species (ions and neutrals). As only electrons are thermalized, their Maxwell-Boltzmann velocity distribution is very different from the ion velocity distribution.[1] When one of the velocities of a species does not follow a Maxwell-Boltzmann distribution, the plasma is said to be non-Maxwellian.