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 Positive and negative sets In measure theory, given a measurable space ("X",Σ) and a signed measure μ on it, a set "A" ∈ Σ is called a positive set for μ if every Σ-measurable subset of "A" has nonnegative measure; that is, for every "E" ⊆ "A" that satisfies "E" ∈ Σ, one has μ("E") ≥ 0. Similarly, a set "A" ∈ Σ is called a negative set for μ if for every subset "E" of "A" satisfying "E" ∈ Σ, one has μ("E") ≤ 0. Intuitively, a measurable set "A" is positive (resp. negative) for μ if μ is