Different approaches to fluid simulation of the longitudinal structure of the atmospheric-pressure microdischarge in helium

Numerical results for different versions of the fluid model of an atmospheric-pressure glow discharge in helium are compared. It is shown that efforts to improve the fluid model are to a large extent prospectless and often even impair previous results. This is because the fluid model has fundamental limitations when describing heavily nonequilibrium media, such as the gas discharge. In such systems, the properties of an ensemble of electrons cannot be reduced to the behavior of an averaged particle, which is characterized by the averaged concentration, averaged directional velocity, and averaged energy (temperature). In particular, the values of the electron temperature in the near-cathode plasma obtained by fluid simulation far exceed both the available experimental data and physical estimates. It is therefore necessary to develop consistent kinetic techniques to correctly describe the behavior of electrons in the near-cathode plasma.