Breakdown of a gas in superimposed d.c. and h.f. electric fields

By means of a time resolution it was found that the electric breakdown of air at atmospheric pressure between a charged plate and a spike, on which a torch discharge is burning, gaves rise to comparatively stable ellipsoidal plasma formations — plasmoids. Their dimensions stay within 2÷10 mm, velocity 0÷4 ms, acceleration –210÷1500 ms^–2. Their life time is 10^–2 s in magnitude. They decay either at the spike electrode, or when the actual breakdown takes place, or they desintegrate in the inter-electrode space.