Corona discharge the electron-liberation is a high-energy photon from an atom within the plasma body relaxing after excitation from an earlier collision. The use of ionized neutral gas as a source of ionization is further diminished in a negative corona by the high-concentration of positive ions clustering around the curved electrode. Under other conditions, the collision of the positive species with the curved electrode can also cause electron liberation. The difference, then, between positive and negative coronas, in the matter of the generation of secondary electron avalanches, is that in a positive corona they are generated by the gas surrounding the plasma
Positive and negative sets there is a partition of "X" into a positive and a negative set; such a partition ("P","N") is unique up to μ-null sets, and is called a "Hahn decomposition" of the signed measure μ. Given a Hahn decomposition ("P","N") of "X", it is easy to show that "A" ⊆ "X" is a positive set if and only if "A" differs from a subset of "P" by a μ-null set; equivalently, if "A"−"P" is μ-null. The same is true for negative sets, if "N" is used instead of "P". Positive and negative sets In measure theory, given a measurable space ("X",Σ)