By Duane Friend
Many people like watching lightning when it’s off in the distance. If it’s close, it becomes a hazard. While fatalities from lightning have come down considerably in the past few decades, there are still several dozen per year that occur in the United States.
We are all aware of this danger. It is electricity! Millions of volts and thousands of amps from one bolt. A direct strike from a lightning bolt is bad news.
Lightning research shows that another type of radiation is given off during thunderstorms that is likely caused by lightning. In some circumstances a Terrestrial Gamma ray Flash, or TGF, is produced.
Gamma rays are a form of electromagnetic radiation. Electromagnetic radiation is the flow of energy in the form of waves that travel through space or substances. It has electrical and magnetic relationships, hence the name. There is a range or spectrum of wavelengths, called the electromagnetic spectrum. Most of these wavelengths are invisible to the human eye, except for a very tiny part called the visible spectrum. The shorter the wavelength on the spectrum, the more powerful it is. Gamma rays are part of the spectrum that have the shortest wavelengths, in the range of one trillionth of a meter or less. Gamma rays are produced by the sun but fortunately by the time solar energy reaches Earth it has been degraded and filtered out. We also associate gamma rays on earth with nuclear explosions, and if you’re a comic book fan, the creation of The Hulk. There is now a recently discovered natural source for gamma radiation, from thunderstorms.
Basically, strong electrical fields associated with lightning near the top of a thunderstorm move electrons upward at extremely high speeds. When these electrons get very close to the nuclei of nitrogen atoms in the air, the electrons slow slightly and emit gamma rays, which move up and out into space, then is picked up by earth’s magnetic field. The flashes are extremely brief, lasting about one thousandth of a second.
Since activity is happening tens of thousands of feet above ground and moving farther up, humans are not in harms way. Airplanes typically don’t fly over thunderstorms and should not be in the direct path of a flash. A study of the potential of a commercial place being in a gamma ray flash estimated the chances are extremely low.
From: NASA
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