The planet’s heat distribution explains why lightning doesn’t strike near the equator
SWRI, JPL-CALTECH/NASA, JUNOCAM
When Voyager 1 revealed lightning on Jupiter in 1979, something about the flashes didn’t make sense. From a distance, it seemed like the radio waves from the massive planet’s lightning bolts didn’t reach the high frequency emitted by lightning on Earth.
But the Juno spacecraft, which has been orbiting much closer to Jupiter’s surface for the last two years, has helped solve the mystery. The radio waves emitted by the planet’s lightning are, in fact, in a similar frequency range as our lightning at home, mission scientists report in the June 6 Nature. Astronomers couldn’t detect anything but the lower frequencies, called “whistlers,” until now.
And while solving that mystery, the researchers discovered another twist: Jupiter’s lightning may have a similar frequency as Earth’s, but it is focused at the planet’s poles instead of nearer to the equator, as on Earth.
“Jupiter continues to surprise us,” says Shannon Brown, a researcher at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., and lead author of the new study. Brown says the difference in location of the lightning strikes has to do with how the two planets distribute heat. Earth receives most of its heat from the sun, and that heat is focused around the equator. Jupiter, much farther from the sun, creates most of its heat internally, leading to different convection patterns that drive lightning to the poles (SN: 3/31/18, p. 10).
Juno had been scheduled to take a mission-ending plunge into Jupiter’s atmosphere in July, but on June 6 the mission was extended for another three years — plenty of time to catch more great lightning shows(SN: 6/24/17, p. 14).