Electric God

New data from NASA’s Juno spacecraft at Jupiter reveals a more chaotic magnetic field around the gas giant than expected, including a “blue spot” of magnetic south near the planet’s equator. (Image credit: Bloxham, Jeremy; Moore, Kimberly (2018)/Figshare (CC BY 4.0))

April 1, 2020

Zeus forges his lightning bolts.

Jupiter is the largest planet, clearly visible in the early April morning sky It is so large that all of the other planets could fit inside its 1.77 X 10^15 cubic kilometer volume. Jupiter rotates in about 10 hours, causing its diameter to be 9275 kilometers more than the distance between its poles. Jupiter reveals an electrical connection between its polar regions and its four largest moons: all of them leave trails in Jupiter’s polar aurorae.

Jupiter is more electrically active than consensus models predicted. Instead of a 5 gauss magnetic field, the giant planet possesses a 9 gauss field, compared to Earth at .5 gauss. The field is also quite irregular, suggesting to astrophysicists that there is a nonconformity in Jupiter’s core.

The Juno mission was launched on August 5, 2011 with a current timeline extending into 2022. Since there are radiation belts around Jupiter, similar to the Van Allen radiation belts that surround Earth, but thousands of times greater in strength and extent, Juno’s electronics are housed within a titanium shell, so that the energetic particles trapped around Jupiter will not interfere with its systems.

As of this date, operations will end in July 2021, with incineration taking place sometime in 2022. The extension is largely due to a concern with its fuel delivery system. Instead of orbiting Jupiter every 14 days, as originally planned, Juno is in a 53 day orbit.

Jupiter possesses a toroidal electromagnetic field extending outward for 650 million kilometers, reaching beyond Saturn’s orbit. Charged particles from the solar wind, as well as from Jupiter, itself, are trapped in its magnetic field, creating a vast plasma sheath similar to the Van Allen belts around Earth. The plasmasphere around Jupiter emits lethal radiation that is thousands of times greater than the Van Allen belts, however.

Juno’s microwave radiometer detected 377 lightning discharges in the megahertz and gigahertz frequency ranges, but the distribution was opposite to what is seen on Earth. Jupiter’s lightning takes place near its poles but none near the equator. This makes sense: its moons are connected to Jupiter’s poles. Since electric charge flows around Jupiter, its moons spin through a dynamic electric field. This generates trillions of watts of electricity, creating the lightning and polar aurorae. It is not convection that drives lightning on Jupiter (or on Earth), it is electricity and plasma dynamics.

Stephen Smith

The Thunderbolts Picture of the Day is generously supported by the Mainwaring Archive Foundation.

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