Jovian Auroras in the Infrared
It was a dark and stormy night.
On Aug. 8, 1997, astronomers at NASA's Infrared Telescope Facility on Mauna Kea in Hawaii were taking routine observations of Jupiter when a magnetic storm struck the distant planet's polar regions. The auroras that grace Jupiter's poles--souped-up versions of the northern and southern lights that shimmer in Earth's upper atmosphere--intensified. For the first time, researchers detected winds of charged particles whipping around the poles like cars around a racetrack.
Known as electrojets, these high-speed winds may explain how energy from the auroral regions spreads around the planet. This energy maintains temperatures throughout the upper atmosphere that are hundreds of degrees higher than what the meager sunlight shining on Jupiter could ever produce.
Jovian auroras are fueled by charged particles, mostly electrons, belched by the planet's volcanically active moon, Io. Captured by the planet's powerful magnetic field, these particles crash into the atmosphere a few hundred kilometers above Jupiter's magnetic poles, where they collide with hydrogen molecules. The battered molecules collect into oval patches centered on the poles and emit ultraviolet light.
Slightly higher in the atmosphere, hydrogen molecules ionized by the incoming electrons combine with hydrogen atoms to become ionized triatomic hydrogen ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]). …