a discharge, frequently luminous, at the surface of a conductor or between two conductors of the same transmission line, accompanied by ionization of the surrounding atmosphere and often by a power loss.
corona discharge
An electrical discharge characterized by a corona, occurring when one of two conducting surfaces (such as electrodes) of differing voltages has a pointed shape, resulting in a highly concentrated electric field at its tip that ionizes the air (or other gas) around it. Corona discharge can result in power loss in the transmission of electric power, and is used in photocopying machines and air-purification devices. See also electric arc.
Saint Elmo's fire (sānt ěl'mōz) Pronunciation Key
A visible and sometimes audible electric discharge projecting from a pointed object, such as the mast of a ship or the wing of an airplane, during an electrical storm. First identified as an electrical phenomenon by Benjamin Franklin in 1749, St. Elmo's fire is a bluish-white plasma caused by the release of electrons in a strong electric field (200 or more volts per cm); the electrons have enough energy to ionize atoms in the air and cause them to glow. The phenomenon appears near pointed objects because electrical fields generated by charged surfaces are strongest where curves are sharpest. It is named after St. Elmo, the patron saint of mariners, as the phenomenon was often observed by sailors during thunderstorms at sea. See also lightning rod.
[el-mohz] 
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