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Fraser
2004-Dec-20, 06:19 PM
SUMMARY: One instrument on board NASA's Cassini spacecraft allows it to detect lightning. As part of initial tests, the spacecraft was able to detect lightning on Earth from a distance of 89,000 km (55,300 miles). As it approached Saturn last July, it began detecting lightning on the Ringed Planet at a distance of 161 million km (100 million miles). This means that lightning on Saturn is 1 million times stronger than on our own planet. One possible reason is because the gas giants could have magnetic fields similar to the Sun, which rotates at different speeds at different latitudes.

View full article (http://www.universetoday.com/am/publish/lightning_storms_saturn.html)

What do you think about this story? Post your comments below.

antoniseb
2004-Dec-20, 06:40 PM
This story covers several interesting topics. One is the item VanderL pointed out in the EU thread, about the extra powerful lightning. Another is the dust density found as Cassini passed through the ring system, and a third was the variation in the magnetic rotation period of Saturn [already previously discussed on the forum].

Concerning the variable magentic rotation period, I think that Cassini will find it is related to the latitude that the shadow of the rings crosses the face of the planet.

ChromeStar
2004-Dec-20, 07:25 PM
Just like to say that it is quiet amazing of shier size of the lighting on saturn, it seems that all the gas planets have the strongest or fastest - neptunes winds are quiet a number of times stronger then here on earth. :o

dave_f
2004-Dec-20, 08:24 PM
Originally posted by antoniseb@Dec 20 2004, 01:40 PM
Concerning the variable magentic rotation period, I think that Cassini will find it is related to the latitude that the shadow of the rings crosses the face of the planet.
The scientists cited in the articles I've read so far mostly think it has something to do with the fact the magnetic pole is in the same alignment as the geographical pole. The idea I suppose is that magnetic poles that are off-center (like Earth's) are "locked" and don't have a lot of leeway with regards to its own rotational period. Saturn's magnetic pole is freer to dictate its own rotational period (or is more easily influenced by outside factors).

I'm just speculating right now. I imagine the smarter-than-myself people are still speculating, too.

GOURDHEAD
2004-Dec-21, 01:01 AM
The following was excerpted from the article:
In contrast, as Cassini approached Saturn, it started detecting radio signals from lightning about 161 million kilometers from the planet. "This means that radio signals from Saturn's lightning are on the order of one million times stronger than Earth's lightning. That's just astonishing to me!" says Gurnett, who notes that some radio signals have been linked to storm systems observed by the Cassini imaging instrument. Is the detection based on average energy over a time interval appreciably longer than that of a lightning strike or is it based on peak energy? Is is probable that the constituents of Saturn's atmosphere require higher ionization energy thresholds hence deliver higher energy strikes. Higher wind speeds could cause strikes to occur more frequently.

dave_f
2004-Dec-21, 02:01 AM
Originally posted by GOURDHEAD@Dec 20 2004, 08:01 PM
Is the detection based on average energy over a time interval appreciably longer than that of a lightning strike or is it based on peak energy? Is is probable that the constituents of Saturn's atmosphere require higher ionization energy thresholds hence deliver higher energy strikes. Higher wind speeds could cause strikes to occur more frequently.
Since they're talking about "first detection" as the spacecraft approached Saturn, that would probably mean they are talking about the peaks (the average wouldn't be measurable until Cassini got closer to the planet). However, I'm sure the average energy output of the lightnight is also quite larger than Earth's by orders of magnitudes. It's probably the result of what you said, in addition to the fact there's a lot more energy in a Saturnian storm than in a Terran one because there aren't any of those pesky continents in the way.