Self-organization refers to the spontaneous generation of spatially or temporally organized patterns in an otherwise disordered system. Self-organization is ubiquitous in plasma physics particularly in the low-pressure regime as observed in astrophysical jets or plasma loaded flux loops that form on the surface of the Sun. In recent times, self-organization in atmospheric pressure plasmas has captured the attention of researchers. Its occurrence has been observed in DBD discharges as well as DC 1 atm glows with liquid electrodes. The mechanism of pattern formation is still not well understood. Here we briefly review the current understanding of pattern formation in DC glows with liquid anode, surveying past work, application areas, theories on mechanisms of formation from the context of reaction diffusion systems, current experimental work and computational progress towards predicting pattern formation.

Optical emission spectroscopy is used to study a 1-atm dc helium glow discharge with a liquid anode to obtain insight into the physical mechanisms underlying observed plasma self-organization at the liquid surface. Plasma column conditions such as gas temperature, electron density, and species composition were determined by means of optical emissions spectroscopy techniques and correlated with the appearance and structure of anode patterns over a broad burning voltage range with fixed flow rate and liquid conductivity. The discharge column was stratified from a species standpoint with the attachment near the liquid surface containing more sodium and water emission, while near the cathode, the predominant emission was from nitrogen and helium. The experiment suggested a complex interplay between the transport of liquid phase species and the actual composition of the plasma, suggesting the importance of processes such as localized boiling and perhaps physical sputtering.

Plasma self-organization on anode surfaces in 1 atm DC glow discharges remains poorly understood. This effort aims to elucidate the nature of self-organization through the experimental study of resulting patterns on liquid anode surfaces with 13 different electrolytes and thus improves our understanding of the underlying physical processes that give rise to self-organization by investigating electrolyte sensitivity. Self-organization pattern formation and behavior were studied as a function of discharge current, solution ionic strength, and their chemical property evaluation. The response of the patterns to variation in these parameters was measured using an imaging camera and optical emission spectroscopy. Observed pattern characteristic length scales for all of the electrolytes were ranged from 2 to 13 mm and typically increased with current over the investigated range of 20–80 mA. Complex self-organized pattern structures not reported to date were also observed. The parameters associated with pattern formation and morphology complexity are discussed and summarized.