Positive Streamers in Ambient Air and a $\hbox{N}_{2}\!:\!\hbox{O}_{2}$ Mixture (99.8 : 0.2)

Photographs show distinct differences between positive streamers in air or in a nitrogen-oxygen mixture (0.2% O ₂ ). The streamers in the mixture branch more frequently, but the branches also extinguish more easily. Probably related to that, the streamers in the mixture propagate more in a zigzag manner, whereas they are straighter in air. Furthermore, streamers in the mixture can become longer; they are thinner and more intense.