The Mystery of Jupiter's Auroras

Fagjun | Published 2017-09-10 13:41

What is powering Jupiter's auroras?



Media by NASA/JPL-Caltech/Bertrand Bonfond



There's something happening on Jupiter that is stumping astronomers, at least for now. Jupiter, like Earth, has periodic auroras. Last year, NASA's Juno spacecraft discovered the first known auroras in the solar system on a planet other than Earth. Though Jupiter is already known for its vividly-colored storms, the discovery that it also had auroras was important, and revealed more about what the gas giant was like. When Juno flew over the magnetic fields above an active aurora, however, astronomers didn't see what they were expecting to see.


The auroras on Jupiter are brighter than those on Earth, and for years, astronomers thought that they had a good grasp on the auroras on the gas giant. Astronomers thought that the same processes that power Earth's brightest auroras power Jupiter's as well. However, it turns out that this isn't actually true. So what does provide the energy for Jupiter's intensely bright auroras?



Understanding Jupiter's Auroras


Media by NASA/JPL-Caltech/Bertrand Bonfond

On Earth, powerful electric fields that build up along Earth's magnetic field lines cause the brightest auroras. There's a downward flow of electrons in the magnetic field due to solar winds. Areas of electric potential, where there are changes in the electric field, push the electrons from solar winds down to the ground. When the electrons collide with atoms in the atmosphere, they lose some of their energy. This results in the undulating bursts of light that we know as auroras.


Because of the planet's size, Jupiter's electric potential wells are 30 times stronger than those on Earth. However, according to a new study, electric potentials aren't what power Jupiter's auroras. “Instead, on Jupiter the brightest aurora are caused by some sort of turbulent acceleration process that we don’t understand very well,” says Barry Mauk, one of the researchers. On Earth, this process powers only the dimmest auroras.


There's something else going on over on Jupiter that powers its brilliant auroras. We just don't know what it is yet. Scientists usually use models based on the processes on Earth as a framework when studying other planets. Many times, this works. Other times, like this one, using an Earth-based model only raised more questions than it answered.



Planetary Physics


Image by NASA, ESA, and J. Nichols (University of Leicester)



"There are hints in our latest data indicating that as the power density of the auroral generation becomes stronger and stronger, the process becomes unstable and a new acceleration process takes over,” says Mauk. “But we'll have to keep looking at the data."


Researchers say that the energies in the auroral regions on Jupiter are “formidable”. The particles that power auroras on Jupiter can help scientists understand the radiation belts on the planet. These radiation belts have been a challenge not only for spacecraft Juno but for upcoming Jupiter missions as well. Radiation can be debilitating, which makes studying them a challenge. However, a better understanding of the radiation belts can help scientists learn more about how to protect spacecraft and astronauts from harsh extraterrestrial conditions. Also, a comparison of Earth and Jupiter processes can tell us more about planetary physics. Thus, finding the energy source of Jupiter's auroras is definitely worth the trouble.


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