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 nonnegative (resp. nonpositive) everywhere on "A". Of course, if μ is a nonnegative measure, every element of Σ is a positive set for μ. In the light of Radon–Nikodym theorem, if ν is a σ-finite positive measure such that |μ| « ν, a set "A" is a positive set for μ if and only if the Radon–Nikodym derivative dμ/dν is nonnegative ν-almost everywhere on "A". Similarly, a negative set is a set where dμ/dν ≤ 0 ν-almost everywhere. It follows from the definition that every measurable subset of a positive or negative set is also positive or negative. Also, the