The storm has caused a 'Great White Spot' on the planet which is visible from the Earth.
Observations from the Cassini spacecraft - combined with images from ground-based telescopes - reveal the electric spectacle which is producing a tempest so intense the flashes are occurring at the rate of up to ten times a second, say researchers whose findings are published in two papers in Nature.
Great White Spots are so-called because they are large enough to be visible by telescope from Earth and
Observations from the Cassini spacecraft - combined with images from ground-based telescopes - reveal the electric spectacle which is producing a tempest so intense the flashes are occurring at the rate of up to ten times a second, say researchers whose findings are published in two papers in Nature.
Great White Spots are so-called because they are large enough to be visible by telescope from Earth and
break out rarely - about once every thirty years.
This outburst began last December as Cassini orbited the usually calm ringed planet while a network of ground-based observers also monitored the storm's evolution.
Planetary scientist Professor Agustin Sanchez-Lavega, of the School of Engineering of Bilbao, and colleagues said: "
Huge storms known as Great White Spots, which are ten times larger than the regular storms, are rarer and occur about once per Saturnian year (29.5 Earth years)."
It is only the sixth time the once-in-a-generation phenomenon - which occurs as spring comes to the 87,000 mile wide planet's northern hemisphere - has been spotted since 1876.
The storm has a latitude and longitude of 6,200 and 10,500 miles respectively - meaning it would spread across half of the Earth.
Dr Georg Fischer, of the Austrian Academy of Sciences in Graz, and colleagues said in a second study: "The visible plume consists of high-altitude clouds that overshoot the outermost ammonia cloud layer owing to strong vertical convection, as is typical for thunderstorms.
"The flash rates of this storm are about an order of magnitude higher than previous ones, and peak rates larger than ten per second were recorded.
"This main storm developed an elongated eastward tail with additional but weaker storm cells that wrapped around the whole planet by February 2011. Unlike storms on Earth, the total power of this storm is comparable to Saturns total emitted power."
They said the appearance of such storms in the northern hemisphere could be related to the change of seasons.
Physicist Professor Peter Read, of Oxford University, reviewed the papers for the journal and said they present "some of the most detailed observations so far of such a dramatic event."
He said: "These observations reveal with great clarity that the GWS comprises a massive complex of convective thunderstorms, upwelling heat energy and moisture from levels deep within Saturn's atmosphere, accompanied by huge and almost continuous lightning discharges.
"It will be a major challenge to the next generation of atmospheric models to predict when (and where) storm clouds will next appear to brood over Saturn's normally bland and hazy face."
This outburst began last December as Cassini orbited the usually calm ringed planet while a network of ground-based observers also monitored the storm's evolution.
Planetary scientist Professor Agustin Sanchez-Lavega, of the School of Engineering of Bilbao, and colleagues said: "
Huge storms known as Great White Spots, which are ten times larger than the regular storms, are rarer and occur about once per Saturnian year (29.5 Earth years)."
It is only the sixth time the once-in-a-generation phenomenon - which occurs as spring comes to the 87,000 mile wide planet's northern hemisphere - has been spotted since 1876.
The storm has a latitude and longitude of 6,200 and 10,500 miles respectively - meaning it would spread across half of the Earth.
Dr Georg Fischer, of the Austrian Academy of Sciences in Graz, and colleagues said in a second study: "The visible plume consists of high-altitude clouds that overshoot the outermost ammonia cloud layer owing to strong vertical convection, as is typical for thunderstorms.
"The flash rates of this storm are about an order of magnitude higher than previous ones, and peak rates larger than ten per second were recorded.
"This main storm developed an elongated eastward tail with additional but weaker storm cells that wrapped around the whole planet by February 2011. Unlike storms on Earth, the total power of this storm is comparable to Saturns total emitted power."
They said the appearance of such storms in the northern hemisphere could be related to the change of seasons.
Physicist Professor Peter Read, of Oxford University, reviewed the papers for the journal and said they present "some of the most detailed observations so far of such a dramatic event."
He said: "These observations reveal with great clarity that the GWS comprises a massive complex of convective thunderstorms, upwelling heat energy and moisture from levels deep within Saturn's atmosphere, accompanied by huge and almost continuous lightning discharges.
"It will be a major challenge to the next generation of atmospheric models to predict when (and where) storm clouds will next appear to brood over Saturn's normally bland and hazy face."
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