Satellites in the right places at the right time may have solved the puzzle of a strange phenomenon high in Earth’s atmosphere.
The so-called proton auroral spots, which glow brightest at ultraviolet wavelengths, occur at altitudes of about 120 kilometers, says Tai Phan, a space physicist at the University of California, Berkeley. The spots occur when protons in the solar wind–the torrent of charged particles streaming from the sun–slam into Earth’s atmosphere.
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