In nature (stars, lightning), plasma coincides with very high temperatures. High temperatures due to the current flow also occur in plasma generation by gas discharge. When a gas is ionised by means of electromagnetic HF fields, the plasma remains cold or is heated only slightly. In the cold plasma, only the free electrons are “hot” which, due to their small mass, can follow the frequency of the high-frequency field. The heavy atoms, ions and radicals are too inert to follow; for this reason, under HF excitation they hardly change their movement, which is the factor determining the temperature.