High Quality Content by WIKIPEDIA articles! Upper-atmospheric lightning or upper-atmospheric discharge are terms sometimes used by researchers to refer to a family of short-lived electrical-breakdown phenomena that occur well above the altitudes of normal lightning and storm clouds. Upper-atmospheric lightning is believed to be electrically induced forms of optical fluorescence. The preferred usage is transient luminous event (TLE), because the various types of electrical-discharge phenomena in the upper atmosphere lack several characteristics of the more familiar tropospheric lightning.