London, September 14 : Scientists, using the Cassini spacecraft’s Magnetospheric Imaging instrument (MIMI), have detected a new, temporary radiation belt at Saturn, located around the orbit of its moon Dione at about 377,000 km from the centre of the planet.

Radiation belts, like Earth’s Van Allen belts, have been discovered at Jupiter, Saturn, Uranus and Neptune.

However, to date, it has only been possible to observe the variability of their intensity at Earth and Jupiter.

Now that Cassini has been orbiting Saturn for more than five years, it has been possible to assess for the first time changes in Saturn’s radiation belts.

An international team of astronomers made the discovery analyzing data from the MIMI’s LEMMS sensor, which measures the energy and angular distribution of charged particles in the magnetic bubble that surrounds Saturn.

“The most dramatic changes have been observed as sudden increases in the intensity of high energy charged particles in the inner part of Saturn’s magnetosphere, in the vicinity of the moons Dione and Tethys”, said Dr. Roussos.

“These intensifications, which could create temporary satellite atmospheres around these moons, occurred three times in 2005 as a response to an equal number of solar storms that hit Saturn’s magnetosphere and formed a new, temporary component to Saturn’s radiation belts”, he added.

The new belt, which has been named “the Dione belt”, was only detected by MIMI/LEMMS for a few weeks after each of its three appearances.

The team believe that newly formed charged particles in the Dione belt were gradually absorbed by Dione itself and another nearby moon, named Tethys, which lies slightly closer to Saturn at an orbit of 295,000 km.

Unlike the Van Allen belts around the Earth, Saturn’s radiation belts inside the orbit of Tethys are very stable, showing negligible response to solar storm occurrences and no variability over the five years that they have been monitored by Cassini.

Interestingly, it was found that the transient Dione belt was only detected outside the orbit of Tethys.

It appeared to be clearly separated from the inner belts by a permanent radiation gap all along the orbit of Tethys.

According to Dr. Roussos, “Outside the orbit of Tethys, the variability of Saturn’s radiation belt might be enhanced in the coming years as we start approaching the solar maximum.”

“If solar storms occur frequently in the new solar cycle, the Dione belt might become a permanent, although highly variable, component of Saturn’s magnetosphere, which could affect significantly Saturn’s global magnetospheric dynamics,” he said. (ANI)