Understanding the interactions between ionized matter and neutral particles is a prerequisite for discovering their impact on natural phenomena. One such phenomenon is the electric wind, which supposedly occurs due to the charged particle–neutral coupling in systems of weakly ionized gases, but this mechanism remains unclear. Here, we report direct evidence that electric wind is caused by an electrohydrodynamic force generated by the charged particle drag as a result of the momentum transfer from electrons/ions to neutrals. The model experiment is based on a pulsed plasma jet as a source of weakly ionized gases generated in the helium gas at atmospheric pressure using Schlieren photography. Studying the helium gas flow trajectories at different discharge parameters allows one to distinguish between the effects of streamer propagation or space charge drift causing the electric wind as well as to determine the role of electrons and (positive) ions in wind generation.

The relationship between the electron excitation temperature (Texc) determined by optical emission spectroscopy and the electron temperature (Te) using a rf-compensated Langmuir probe was investigated in argon capacitively coupled plasmas. In the experiment performed at the gas pressure range of 30 mTorr to 1 Torr and the rf power range of 5–37 W, the electron energy probability function (EEPF) obtained from the probe current versus voltage characteristic curve showed two energy groups of electrons. The measured EEPF demonstrated that the electron energy distribution changed from Druyvesteyn to single Maxwellian as the discharge current was increased and from bi-Maxwellian to Druyvesteyn as the pressure was increased. As a result, Texc showed a tendency identical to that of Te of the high energy part of electrons as pressure and rf power were varied. This suggests that electron temperature can be determined from the measured Texc through a calibration experiment by which the ratio between electron and excitation temperatures is measured.