Explosions on Jupiter’s Polar Auroras –“Triggered By Moon Io’s Massive Volcanic Activity”

 

 

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On Earth, bursts of particles spewed by the Sun spark shimmering auroras, like the Northern Lights, that briefly dance at our planet’s poles. But, on Jupiter, there’s an auroral glow all the time, and new observations show that this Jovian display sometimes flares up because of a process having nothing to do with the Sun.


In this artist’s rendering below from the Japan Aerospace Exploration Agency, flows of electrically charged ions and electrons accelerate along Jupiter’s magnetic field lines (fountain-like blue curves), triggering auroras (blue rings) at the planet’s pole. Accelerated particles come from clouds of material (red) spewed from volcanoes on Jupiter’s moon Io (small orb to right) –the volcanic epicenter of our solar system. Recent observations of extreme ultraviolet emissions from Jupiter by satellite Hisaki (left foreground) and the Hubble Space Telescope (right) show episodes of sudden brightening of the planet’s auroras. Interactions with the excited particles from Io likely also fuel these auroral explosions, new research shows, not interactions with particles from the Sun.

 

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Jupiter watchers have long known that the giant planet’s ever-present polar auroras – thousands of times brighter and many times bigger than Earth – are powered by both electrically charged particles from the Sun colliding with Jupiter’s magnetic field and a separate interaction between Jupiter and one of its many moons, called Io. But there are also auroral explosions on Jupiter, or periods of dazzling brightening, similar to auroral storms on Earth, that no one could definitively trace back to either of those known causes.

In the aurora-making interaction of Jupiter and Io, volcanoes on the small moon blast clouds of electrically charged atoms (ions) and electrons into a region surrounding Jupiter that’s permeated by the planet’s powerful magnetic field, thousands of times stronger than Earth’s. Rotating along with its rapidly spinning planet, the magnetic field drags the material from Io around with it, causing strong electric fields at Jupiter’s poles. The acceleration of the ions and electrons produce intense auroras that shine in almost all parts of the electromagnetic spectrum but most brightly in high-energy bands, like ultraviolet light and X-rays, that are invisible to unaided human eyes.

 

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Io is the only known place in the Solar System with volcanoes erupting extremely hot lava like that seen on Earth. Because of Io's low gravity, large volcanic eruptions produce an umbrella of debris that rises high into space. Such outbursts can send material hundreds of miles above the surface.

The recent eruptions resemble past events that spewed tens of cubic miles of lava over hundreds of square miles in a short period of time. All three events, including the largest, most powerful eruption of the trio on 29 August, 2013, were likely characterized by “curtains of fire," as lava blasted out of fissures perhaps several miles long.

The 29 August, 2013, outburst on Io shown below was among the largest ever observed on the most volcanically active body in the solar system. Infrared image taken by Gemini North telescope. Image credit: Katherine de Kleer, UC Berkeley.

 

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The brightest eruption at a caldera named Rarog Patera, was calculated to have produced a 50 square-mile, 30ft thick lava flow, while another close to a caldera called Heno Patera, produced flows covering 120 square miles. Both were located in Io's southern hemisphere, near its limb, and were nearly gone when imaged five days later.

Now, new observations of the planet’s extreme ultraviolet emissions show that bright explosions of Jupiter’s aurora likely also get kicked off by the planet-moon interaction, not by solar activity. A new scientific paper about these observations by Tomoki Kimura of the Japan Aerospace Exploration Agency (JAXA), in Sagamihara, Kanagawa, Japan, and his colleagues, was published online today in Geophysical Research Letters, a journal of the American Geophysical Union.

Starting in January 2014, a telescope aboard the JAXA’s Hisaki satellite, which focused on Jupiter for two months, recorded intermittent brightening of the giant planet’s aurora. The telescope detected sudden flare-ups on days when the usual flow of charged particles from the Sun, known as the solar wind, was relatively weak.

Additional space and ground-based telescopes, including the Hubble Space Telescope, also viewed Jupiter during these lulls in the solar wind. Both Hisaki and Hubble witnessed explosions of the planet’s aurora despite the solar wind’s calm, suggesting that it’s the Jupiter-Io interaction driving these explosions, not charged particles from the Sun, according to the new study. The new research does not address exactly what is happening in the Jovian magnetosphere to cause the temporary brightening of auroral explosions.

The Daily Galaxy via AGU

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