A Distinct Class of High Peak-Current Lightning Pulses Over Mountainous Terrain in Thunderstorms

Cloud-to-ground strokes, narrow bipolar events, and energetic in-cloud pulses are known classes of high peak-current lightning processes that occur in thunderstorms. Here, we report one more distinct class of high peak-current events observed exclusively over mountainous terrain, usually above 2,000 m altitude, in the continental Unites States. These events, which we call mountain-top energetic pulses (MEPs), are bipolar pulses with negative radiated field polarities. MEPs are generated between the high mountain tops and compact overhead thunderclouds. Evidence supports the hypothesis that MEPs are produced by terrain-initiated upward positive leaders propagating in high electric fields due to the proximity of the low negative charge regions of the thunderstorms. This scenario further suggests the possibility that MEPs are associated with downward terrestrial gamma-ray flashes, and their high peak currents imply that they may produce elves.