High-altitude atmospheric flashes (sprites and jets)

SpaceWeb@SkyNet.oulu.fi - last update: 28 May 1995, 1650 UT
One of the strangest new findings in Earth's atmosphere are the flashes found high above the thunderstorm clouds. Although the clouds themselves are at low altitudes to be important for ionospheric physics, the flashes can reach altitudes of about 90 km, i.e., the ionospheric E-region, and can thus be relevant also for space physics. The flashes seem to occur all around the world at a rate of at least one flash per minute. They have a life time measured in milliseconds. In addition, it seems that there are two types of flashes: Another type of strange flash has also been seen: Observed emissions are most likely byproducts of the ionization processes of nitrogen and oxygen (the main molecules at these altitudes), which takes place because of the flashes. Details of the process are, however, still unknown.

One of the models suggested to explain these observation starts from a single cosmic ray colliding into an air molecule, and sparking a runaway atmospheric breakdown.

Other, possibly related events, are twin bursts of radio energy, or transionospheric pulse pairs, TIPP, and gamma ray flashes. They have also been associated with thunderstorms.

Source: High-Altitude Flashes Mystify Scientists in EOS, 75, Number 51, 1994

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