Thermal vs Non-Thermal Plasmas
The classification of plasmas based on thermodynamic equilibrium between electron temperature T_e and heavy ion/gas temperature T_i.
Governing formula
Thermal: T_e ≈ T_i ≈ T_gas; Non-Thermal: T_e ≫ T_i ≈ T_gas
SI unit
Kelvin or eV
In depth
Thermal (hot) plasmas (like fusion cores or arc discharges) are in local thermodynamic equilibrium (T_e ≈ T_i ~ 10⁴–10⁸ K). Non-thermal (cold) plasmas (like fluorescent tubes or atmospheric plasma jets) have high electron energy (T_e ~ 10,000 K) while ions remain near room temperature (T_i ~ 300 K).
Examples in the real world
Cold atmospheric plasmas processing temperature-sensitive polymer surfaces and living skin tissue.