Spatial–Temporal Evolution and Plasma Parameters’ Diagnosis of a Transverse Glow Discharge in Atmospheric Pressure Air

A stationary transverse discharge excited by an alternating current voltage is generated downstream of two needle electrodes perpendicular to flowing air lower than 4.1 L/min. The results show that under a constant peak current, the discharge length increases with increasing the air flow rate. Under a constant flow rate, it becomes fatter and brighter with increasing the peak current. Through the voltage-current characteristics, it is found that the transverse discharge operates in a normal glow regime under a lower peak current and an abnormal glow regime under a higher peak current. The critical peak current from the normal glow transiting to the abnormal glow increases with increasing the air flow rate. By fast photography, it is found that, no matter which regime it is in, an emission channel always bridges the two electrodes. However, its emission intensity varies with time during one voltage cycle. This suggests that abundant charges and active species always exist in the channel. It is also found that characteristic regions can be observed for the normal glow discharge, which consist of a positive column, a Faraday dark space (FDS), and a negative glow (NG) at the voltage peak moment. NG alternately appears in the vicinities of the two electrodes. Compared with the normal glow discharge, FDS is absent, and the anode glow is more noticeable for the abnormal glow discharge. Based on the optical emission spectroscopy, the electron temperature, the vibrational temperature, the rotational temperature, and the electron density are investigated.