Mystery of Aurora on Saturn solved by never-before-seen mechanism? NASA probe first raised issue

tech.hindustantimes.com:

Saturn is the sixth planet in the solar system which has extremely large and bright rings around it. Now, Leicester space scientists have discovered a never-before-seen mechanism fuelling huge planetary aurora on Saturn. The study was published in in 'Geophysical Research Letters'. Saturn is unique among planets observed to date, in that some of its aurorae are generated by swirling winds within its own atmosphere, and not just from the planet's surrounding magnetosphere. At all other observed planets, including Earth, aurorae are only formed by powerful currents that flow into the planet's atmosphere from the surrounding magnetosphere. These are driven by either interaction with charged particles from the Sun (as at the Earth) or volcanic material erupted from a moon orbiting the planet (as at Jupiter and Saturn).

This discovery changed scientists' understanding of planetary aurorae and answers one of the first mysteries raised by NASA's Cassini probe, which reached Saturn in 2004: why can't we easily measure the length of a day on the Ringed Planet?

When it first arrived at Saturn, NASA probe Cassini tried to measure the bulk rotation rate of the planet, that determines the length of its day, by tracking radio emission 'pulses' from Saturn's atmosphere. To the great surprise of those making the measurements, they found that the rate appeared to have changed over the two decades since the last spacecraft to have flown past the planet - Voyager 2, also operated by NASA - in 1981.

Leicester PhD researcher Nahid Chowdhury is a member of the Planetary Science Group within the School of Physics and Astronomy and corresponding author for the study.

He said, "Saturn's internal rotation rate has to be constant, but for decades