By Sid Perkins
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. Scientists have suggested that when the planet’s protective magnetic field is disrupted, these high-energy protons break through and can reach the atmosphere. The satellite data gathered last year bolster that scenario.