Striated air discharges, characterized by periodic bright and dark patterns along the discharge axis, are manifestations of self-organized plasma instabilities arising from the non-linear coupling of ionization, energy transport, and space charge dynamics. In this work, an experimental investigation of direct current air striation plasma formation under low-pressure conditions was conducted. The effects of discharge current, pressure, and an externally applied transverse magnetic field on the striation patterns were examined. It was observed that decreasing the discharge current or increasing the pressure enhances the number of the striations, accompanied by a decrease in the average striation wavelength, while external transverse magnetic field promotes discharge pattern regularity through electron confinement. Distinct from inert gases, air striated discharge exhibits a weaker pressure dependence of the striation wavelength, which originates from strong inelastic collisional energy losses in molecular species. Optical emission spectroscopy analysis revealed that the bright discharge regions are dominated by the N2 second positive system, indicating a quasi-neutral, low-electric field environment in the positive column, where electron–neutral collisions sustain excitation rather than ionization. Spatially resolved measurements demonstrated periodic oscillations of the reduced electric field, electron temperature, and electron density along the discharge axis. A distinct phase shift between the oscillations of these discharge parameters confirms the existence of an ionization transport feedback loop that sustains stationary ionization waves. The formation of striated air plasma originates from a self-sustained ionization instability regulated by local field enhancement and space charge modulation. The study provides a new perspective for understanding striation generation in molecular gas discharges and offers valuable insights for controlling plasma uniformity in low-pressure discharge systems.
Dong et al. (Mon,) studied this question.