I have been doing some introductory reading on plasma physics as part of my research, and I am currently trying to understand the concept of electron temperature. Based on my basic understanding, electron temperature is a measure of the average thermal velocity of the electrons in the plasma.
From my background in high-temperature gas dynamics, I know that the internal energy of each species (above the zero point) is distributed among translational, rotational, vibrational, and electronic modes. The electronic mode represents the kinetic and potential energy of electrons in their orbits within the atom.
I recall that in a state of vibrational non-equilibrium, a gas can have a "vibrational temperature" significantly different from the translational-rotational temperature to account for the energy in the vibrational mode. Drawing a parallel, I am considering that "electron temperature" might similarly account for the energy in the electronic mode (energy of bound electrons).
However, I understand that plasma is a mixture of neutral particles, ions, and free electrons. During the plasma heating process, free electrons acquire energy. The literature leaves some ambiguity, so I would like to understand if electron temperature refers only to free electrons or if it is a measure of the average energy possessed by all electrons (both bound and free) within the plasma.
