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Masaki Fukushima, Institute for Cosmic Ray Research at the University of Tokyo.
This solar-powered, tablelike scintillation detector at the Telescope Array cosmic ray observatory measures the strength and direction of “air shower” particles that fall to earth after incoming cosmic ray particles hit gas molecules in the atmosphere. In a major experiment, 507 of the observatory’s 523 scintillation detectors — spread out over 300 square miles of Utah desert — were used to find a “hot spot” in the northern sky that is emitting a greater-than-expected number of ultrahigh-energy cosmic rays.

SALT LAKE CITY — International researchers using a remote high desert location in Millard County caught lightning in a bottle — sort of — not once but 10 times.

Instruments recorded bursts of gamma ray flashes produced in the first milliseconds of cloud-to-ground lightning strikes.

The showers, called terrestrial gamma-ray flashes, happened two to three miles above the ground and were documented 10 times between 2014 and 2016 — representing more events than have been observed in rest of the world combined.

Gamma rays are the most energetic form of electromagnetic radiation.

The Telescope Array Lightning Project is the first to detect the downward flashes at the beginning of cloud-to-ground lightning and to show where they originated in thunderstorms.

John Belz, professor of physics at the University of Utah and principal investigator with the lightning project, said gamma ray flashes have been seen from satellites orbiting the Earth for 20 years.

"Thousands of these things have been seen by satellites," he said, but they are detected from hundreds of miles away.

Laura Seitz, Deseret News
Lightning strikes over Salt Lake City on Monday, June 15, 2015.

Belz said only a third of lightning occurs in cloud-to-ground strikes. The rest are within a singular cloud or from cloud to cloud.

Satellites are observing the "upward" flashes of gamma rays, while the telescope array in Millard County recorded the gamma ray showers in downward earthstrikes.

Previously, only six downward gamma ray flashes have ever been recorded, two of which came from artificially induced lightning experiments.

Until a satellite recorded the first terrestrial gamma ray flash in 1994, physicists thought only violent celestial events, such as exploding stars, could produce the gamma rays.

Over time, scientists have determined that the rays were produced in the initial milliseconds of upward intracloud lightning, which beamed the rays into space. Since discovering the upward flashes, physicists wondered whether cloud-to-ground lightning produced similar flashes that beam downward.

The work in Utah's desert has confirmed the downward flashes of gamma rays early in the lightning strike.

"We might actually learn something about the origin of lightning from this," Belz said.

The Telescope Array Surface Detector where this work unfolded is a 300-square-mile cosmic ray observatory in Millard County. It features 507 scintillator detectors, or high-energy particle detectors.

Ben Stokes, University of Utah
In this time-lapse photo, stars appear to rotate above the Middle Drum facility of the Telescope Array, a $25 million cosmic ray observatory that sprawls across the desert west of Delta, Utah. Physicists from the University of Utah, University of Tokyo and elsewhere report the observatory has detected a “hot spot” in the northern sky emitting a disproportionate number of ultrahigh-energy cosmic rays, which are the most energetic particles in the universe. The discovery of a hot spot is a step in the long quest to discover the source or sources of the most powerful cosmic rays.

The area was selected for its flat terrain, low humidity, dark night skies and proximity to the University of Utah — the leading research institution in the arena of high-energy cosmic rays, possessing the world's largest data set.

The study of cosmic ray showers and how they propagate through space before arriving on Earth is expected to assist scientists in their attempts to unravel the evolution of the universe.

Belz said the telescope array is project designed to study particles from other galaxies and the effects of violent astrophysical events millions of light years away.

While Belz said that field of study is admittedly arcane and esoteric, lightning is something more familiar to people.

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"We've all seen the strikes and heard the thunder," he said. "We are adding a piece of information and using this detector designed to understand remote astrophysical objects and gaining information to learn more about nearby or common phenomena that everybody is familiar with."

The research on gamma ray flashes was published in the Journal of Geophysical Research: Atmospheres earlier this month. Along with the University of Utah, the team of scientists includes researchers from Japan, South Korea, Russia and Belgium.