1. Electrical phenomena, regarded collectively, that occur in the earth's atmosphere. These phenomena include not only such striking manifestations as lightning and St. Elmo's fire, but also less noticeable but more ubiquitous effects such as atmospheric ionization, the air– earth current, and other quiescent electrical processes. The existence of separated electric charges in the atmosphere is a consequence of many minor processes (spray electrification, dust electrification, etc. ) and a few major processes (cosmic-ray ionization, radioactive-particle ionization, and thunderstorm electrification). The details of thunderstorm charge separation are poorly understood. The maintenance of the prevailing atmospheric electric field is now widely believed to be due to thunderstorm effects. 2. The study of electrical processes occurring within the atmosphere.