![]() ![]() "The radiation from dark lightning is not something that people need to be frightened about, and it is not a reason to avoid flying. "Doses never seem to reach truly dangerous levels," Dwyer noted. Moreover, the plane would have to be in exactly the wrong place at the wrong time to see such high doses. In addition, the flashes behind the biggest doses of radiation are probably much less common than normal lightning. Still, Dwyer noted the radiation risk posed by these flashes is minimal. This means that commercial airliners may pass through the potentially dangerous altitude of 16,000 feet (4,900 m) twice per flight. The average cruising altitude of a passenger jet ranges from about 30,000 to 40,000 feet (9,150 to 12,200 m). "On rare occasions, according to the model calculations, it may be possible that hundreds of people, without knowing it, may be simultaneously receiving a sizable dose of radiation from dark lightning." However, near the middle of the storms, at about 16,000 feet (4,900 meters) in altitude, "the radiation dose could be about 10 times larger, comparable to some of the largest doses received during medical procedures and roughly equal to a full-body CT scan," Dwyer said.Īlthough airline pilots already do their best to avoid thunderstorms, "occasionally aircraft do end up inside electrified storms, exposing passengers to terrestrial gamma-ray flashes," Dwyer said. Near the tops of thunderstorms, at about 40,000 feet (12,200 meters) in altitude, the scientists calculated that radiation doses are comparable to about 10 chest X-rays, or about the same dose people receive from natural background sources of radiation over the course of a year. Dark lightning does so as well, and since much higher energy particles are involved, it reduces voltage far more quickly, so the electric fields within them "can collapse in a few tens of microseconds," Dwyer said.Īrmed with a model that potentially explains these gamma-ray flashes, Dwyer and his colleagues analyzed how much radiation airline passengers might receive from them. Ordinary lightning arcs from one spot to another to reduce the voltage growing within clouds. These high-energy particles collide into still more air molecules, generating more gamma rays, ultimately explaining many of the properties of the gamma-ray flashes that scientists have detected from thunderstorms. In turn, these gamma rays generate electrons and their antimatter counterparts, known as positrons. These electrons slam into air molecules, producing gamma rays. ![]() In contrast, dark lightning involves high-energy electrons. Normal lightning involves slow electrons that carry electric current to the ground or within clouds. "I find it amazing that it took us two-and-a half centuries after Ben Franklin to find out that there is another kind of lightning inside thunderstorms," Dwyer told LiveScience. Although they may blast out large numbers of gamma rays, they generate very little visible light, leading scientists to call the phenomenon "dark lightning." Now computer models suggest the flashes are caused by an extreme form of lightning. ![]()
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