Auroras on Jupiter

Aug. 23, 2022: Yesterday, NASA released the first James Webb Space Telescope (JWST) images of auroras on Jupiter. The red rings of light circling Jupiter’s poles were big enough to swallow Earth:

Image credit: JWST’s Near-Infrared Camera (NIRCam). The camera’s F360M filter picked up the 3.3 – 3.6 micron glow of excited H3+ in Jupiter’s auroral zone.

But Jupiter’s auroras are more then just oversized versions of our own. They are formed in a completely different way. One of the key ingredients is volcanoes, and–so much for space weather–solar activity is not required.

For the most part, Jupiter makes its own Northern and Southern Lights. It does this by spinning–like crazy. Jupiter turns on it axis once every 10 hours, dragging its giant planetary magnetic field around with it. Spinning a magnet is a great way to generate a few volts; kids do it all the time for science fair projects. Jupiter’s spin produces 10 million volts around its poles.

These voltages set the stage for non-stop auroras. The fuel comes from Jupiter’s volcanic moon Io, where active vents spew ions such as O+ and S+ into Jupiter’s magnetosphere. Polar electric fields grab these ions and slam them into Jupiter’s upper atmosphere. The resulting glow can be seen almost anytime JWST wants to look. Jupiter’s volcano-powered auroras are usually “on.”

Above: This JWST image of Jupiter and its surroundings uses a different color table, so the auroras look blue. They are still infra-red.

Solar wind and CMEs can also help. However, solar storm clouds are naturally weakened by the time they travel all the way to Jupiter, five times farther from the sun than Earth. Also, Jupiter’s powerful magnetic field forms a potent shield. Io is already inside Jupiter’s “defenses,” so it can be more effective.

Two distinct auroras coexist over the poles of Jupiter: Ultraviolet auroras created by atmospheric hydrogen in its molecular form (H2) and infrared auroras created by the hydrogen ion H3+. JWST saw the infrared variety. In fact, the telescope is well instrumented to monitor these auroras. Its Near-Infrared Camera (NIRCam) has a filter that nicely captures the 3.3 to 3.6 micron glow of H3+.

NASA, we want more!

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