39-Year old mystery of Jupiter’s lightning has been solved now

The ways in which lightning on Jupiter is actually analogous to Earth's lightning.

This artist's concept of lightning distribution in Jupiter's northern hemisphere incorporates a JunoCam image with artistic embellishments. Data from NASA's Juno mission indicates that most of the lightning activity on Jupiter is near its poles. Image credit: NASA/JPL-Caltech/SwRI/JunoCam
This artist's concept of lightning distribution in Jupiter's northern hemisphere incorporates a JunoCam image with artistic embellishments. Data from NASA's Juno mission indicates that most of the lightning activity on Jupiter is near its poles. Image credit: NASA/JPL-Caltech/SwRI/JunoCam

Since 1979, when the NASA’s Voyager 1 spacecraft flew past Jupiter, scientists were in wonder about the origin of Jupiter’s lightning, Jovian lightning. Previous studies suggested the lightning-associated radio signals didn’t match the details of the radio signals produced by lightning here at Earth.

Now, researchers from NASA‘s Juno mission depict the manners by which lightning on Jupiter is really practically equivalent to Earth’s lightning. In spite of the fact that, in some ways, the two kinds of lightning are polar opposites.

Enter Juno, which has been orbiting Jupiter since July 4, 2016. Among its suite of highly sensitive instruments is the Microwave Radiometer Instrument (MWR), which records emissions from the gas giant across a wide spectrum of frequencies.

Shannon Brown of NASA’s Jet Propulsion Laboratory in Pasadena, California, a Juno scientist said, “No matter what planet you’re on, lightning bolts act like radio transmitters — sending out radio waves when they flash across a sky. But until Juno, all the lightning signals recorded by spacecraft [Voyagers 1 and 2, Galileo, Cassini] were limited to either visual detections or from the kilohertz range of the radio spectrum, despite a search for signals in the megahertz range. Many theories were offered up to explain it, but no one theory could ever get traction as the answer.”

“In the data from our first eight flybys, Juno’s MWR detected 377 lightning discharges. “They were recorded in the megahertz as well as gigahertz range, which is what you can find with terrestrial lightning emissions. We think the reason we are the only ones who can see it is because Juno is flying closer to the lighting than ever before, and we are searching at a radio frequency that passes easily through Jupiter’s ionosphere.”

“The revelation showed how Jupiter lightning is similar to Earth’s, the new paper also notes that where these lightning bolts flash on each planet is actually quite different.”

“Jupiter lightning distribution is inside out relative to Earth. There is a lot of activity near Jupiter’s poles but none near the equator. You can ask anybody who lives in the tropics — this doesn’t hold true for our planet.”

Jupiter’s orbit is five times more remote from the Sun than Earth’s orbit, which implies that the giant planet gets 25 times less sunlight than Earth. In any case, despite the fact that Jupiter’s atmosphere infers the more of its heat within the planet itself, this doesn’t render the Sun’s beam irrelevant. They do offer some warmth, warming up Jupiter’s equator more than the poles – similarly as they warm up Earth.

According to scientists, this heat at Jupiter’s equator is just enough to create stability in the upper atmosphere, inhibiting the rise of warm air from within. The poles, which don’t have this upper-level warmth and thus no atmospheric stability, enable warm gases from Jupiter’s inside to rise, driving convection and hence making the elements for lightning.

But another question looms. Even though we see lightning near both poles, why is it mostly recorded at Jupiter’s north pole?

In a second Juno lightning paper published today in Nature Astronomy, scientists have shown the largest database of lightning-created low-frequency radio outflows around Jupiter (whistlers) to date. The dataset of in excess of 1,600 signs, gathered by Juno’s Waves instrument, is right around 10 times the number recorded by Voyager 1. Juno distinguished peak rates of four lightning strikes for every second, which is six times higher than the peak values identified by Voyager 1.

Scott Bolton, principal investigator of Juno from the Southwest Research Institute, San Antonio said, “These discoveries could only happen with Juno. Our unique orbit allows our spacecraft to fly closer to Jupiter than any other spacecraft in history, so the signal strength of what the planet is radiating out is a thousand times stronger. Also, our microwave and plasma wave instruments are state-of-the-art, allowing us to pick out even weak lightning signals from the cacophony of radio emissions from Jupiter.”

NASA’s Juno spacecraft will make its 13th science flyby over Jupiter’s mysterious cloud tops on July 16.