NASA scientists reveal how high-energy particles penetrate Earth's atmosphere

Nov. 16 (UPI) -- Earth's magnetic fields shields Earth and its atmosphere from most of the radiation emitted by the sun. But some high-energy particles sneak into the upper atmosphere, causing colorful auroras near the poles.

Thanks to new data collected by a pair of NASA missions tasked with studying Earth's magnetosphere, scientists now have a better understanding of how and why these high-energy electrons cascade into the upper layers of the atmosphere.

Most of the time, energetic electrons supplied by solar winds remain trapped in Earth's magnetosphere -- specifically, the Van Allen Radiation Belts. But occasionally, large swaths of Earth's electromagnetic protective shield become suddenly free of electrons.

Previous studies suggest the missing electrons flood into the upper atmosphere. The latest research -- published this week in the journal Geophysical Research Letters -- offers an explanation for what triggers the cascade.

According to the new data, common plasma waves formed by fluctuating electric and magnetic fields cause electrons to suddenly flood into Earth's atmosphere. The fluctuations are also known as whistler waves, due to their unique sonic signature.

The revelation was made possible by NASA's Van Allen Probes mission and FIREBIRD II CubeSat, which were both at the right place and right time to observe the sudden loss of electrons.

"Observing the detailed chain of events between chorus waves and electrons requires a conjunction between two or more satellites," Aaron Breneman, researcher at the University of Minnesota in Minneapolis, said in a news release. "There are certain things you can't learn by having only one satellite -- you need simultaneous observations at different locations."

The two satellites were able to observe the cascade of electrons from different vantages. On Jan. 20, 2016, the FIREBIRD II CubeSat witnessed the flood of electrons escaping the radiation belts, called microbursts, from below, while the NASA's Van Allen Probes recorded a series of plasma waves just prior to the microburst.

Researchers hope similar observations in the future will reveal more details about the exact mechanics of the scattering of high-energy electrons.