Across
the atmosphere of Earth, lightning flashes about 50 times per second. That’s
4.3 million times a day and roughly 1.5 billion times a year. Using a new
instrument on the International Space Station (ISS), scientists are hoping to
observe and dissect at least a few of those lightning bolts every day.
Launched
to the ISS in August 2013, the Firestation instrument includes photometers to
measure lightning flashes, radio antennas to measure the static (a proxy for
the strength of the electrical discharge), and a gamma-ray electron detector. Firestation
could observe about 50 lightning strokes per day as it looks for brief bursts
of gamma rays that are emitted by some of them.
Gamma
radiation is usually associated with exploding stars or nuclear fusion, but
scientists have found evidence that terrestrial gamma-ray flashes (TGFs) may
occur in the atmosphere as often as 500 times a day. Atmospheric scientists are
interested in the processes that trigger lightning within thunderstorms and
what kinds of lightning produce gamma rays. TGFs may also be related to the
atmospheric phenomena known as red sprites, electrical discharges that extend
upward from thunderstorms.
“The fact that TGFs exist at all is amazing,” said Doug Rowland, the
principal investigator for Firestation and a space physicist at NASA’s Goddard
Space Flight Center. “The electron and gamma-ray energies in TGFs are usually
the domain of nuclear explosions, solar flares, and supernovas. What a surprise
to find them shooting out of the cold upper atmosphere of our own planet.”
The
photograph above, snapped by an astronaut aboard the International Space
Station on December 12, 2013, shows a white flash of lightning amidst the
yellow city lights of Kuwait and Saudi Arabia. Another astronaut orbiting over
Bolivia captured a close-up of a lightning flash beneath a thunderhead on
January 9, 2011 (image below).
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