You know about gamma rays, right?  Those rays that come boiling across billions of light years from rapidly rotating, high-mass stars collapsing into black holes.  We see flashes of gamma rays being emitted in nuclear blasts. We know that if a gamma ray burst from relatively close-up were pointed at the Earth, prospects for the continuation of life become very bleak, very rapidly.  Overall, lifeforms exposed to gamma radiation suffer severe limitations to their likelihood of a future.  All things considered, it seems a pretty good idea to avoid gamma rays.

Well, guess what:  Gamma rays are produced right here on Earth.  Not from radioactive decay (although that certainly does produce gamma rays), not from proximity to collapsing stars.  It happens about 50 times around the globe every day.  Know what causes it?  I’ll give you a hint:

Image:  John R. Southern (some rights reserved)

Lightning.

Unknown until 1994, NASA’s Gerald Fishman discovered Terrestrial Gamma-Ray Flashes (TGFs) by accident, while documenting extraterrestrial gamma ray bursts at Compton Gamma Ray Observatory.

Lasting only about 1 millisecond, but more powerful than the gamma rays emmitted by the sun, the radiation fountains up to be released into space from surprisingly low altitudes.  Not every lightning strike you see is believed to produce gamma rays.  The current theory involves a complicated chain of events called the “Relativistic Runaway Breakdown Theory”.  I don’t know about you, but that sounds rather ominous to me.  “Runaway breakdown”?  After you chew on that for a while, you’ll be excited to learn that scientists now believe that some of the radiation isn’t released to space, but channeled back down to lower altitudes.

Lightning does a lot of strange and interesting things above the clouds.  Sprites, elves, blue jets, and now gamma ray flashes.  Beautiful and awe-inspiring as it is from the Earth, next time you’re in a thunderstorm just think what’s happening on the other side of the clouds… in space.

Red Sprites  Image:  D. Sentman, G. Wescott, Geophysical Institute,
U. Alaska Fairbanks, NASA

NASA has several videos up on YouTube showing lightning from space, like this one,
A little long, but it slows the action down to 5fr per second.   This one shows sprites, and is really interesting.