Not sure whether to post this here or in the Astronomy Science Forum. Posted here as there have been several Saturn images posted over the last month or so that had the EZn cloud system in them.
Back on 25/01/2009 I posted images and an animation of possible new storm structure on Saturn. As most here know, I am part of an international team regularly contributing data to Dr Georg Fischer.
I thought the info Georg supplied to me this morning may be of general interest.
Attached is an image taken by Cassini 27/01/2009 that Georg refers to.
Dr Georg Fischer is recognized as a world leading authority on this subject.
Georg is currently in Graz Austria, he works for the Space Research Institute at the Austrian Academy of Sciences
Explanation of terms;
SED's = Saturn Electrostatic Discharge
RPWS = Radio & Plasma Wave Science, refers to the instrument onboard the Cassini space craft that detects SED's, that is lightning in the atmosphere of Saturn.
Regards
Trevor
Hi Trevor,
I have heard in the news about this terrible heat wave in Australia. When I look out the window of my office it is just snowing here....so hopefully it will get cooler soon in Down Under.
The last SEDs RPWS detected are from January 27, but as you know, that does not mean that the storm must be over. I have attached you a Cassini image also from January 27, and the cloud system can be still seen pretty good (on the right side in the middle).
This long-lived cloud system in the equatorial zone is quite interesting, although, up to now, there still seems to be no lightning coming from there. Maybe this will change soon. When the Voyagers were at Saturn, soon 29 years ago, there was also equinox, so it was exactly the same season. And both Voyagers detected SEDs (in Nov. 1980 and August 1981) from an equatorial storm system. This system was not imaged, but from the periodicity of SED episodes around 10 hours 10 min., the equatorial region was the only possible source. So I kind of expect the development of a long-lived equatorial storm system. The occurrence of SED storms in the various latitudinal bands could be related to seasonal effects. One reason for an equatorial storm around equinox could be the sharp ring shadow, causing temperature gradients and possibly triggering storms in Saturn's atmosphere.
Trevor, very interesting. I had a good close look at the piccie and I've picked up on what might be a couple of other disturbances in the making. I circled them...and the current one as well for people to see. Take a look and let me know what you think.
I believe the large elongated cloud system (circled by renormalised) is the storm system that SED's were detected from, pre Jan 27th.
Don't think this image shows the EZn region where the long lived cloud system that Georg speaks of, currently is.
The other smaller oval features are consistent with features seen on previous high res images released by the Cassini Imaging team.
I don't think this particular image has been publicly released, it has been made available to Georg for his research purposes. Normally when they release images they have done a lot off work on them before hand.
I thought it would be interesting to see the sort of image the Cassini cameras produce, that probably don't get public airing. I think it is interesting to be up with the latest thinking on this subject.
That large one I circled, almost reminds of a phenomenon called the island effect. You see it it sometimes from satellite imagery taken over the ocean. On the lee side of islands you sometimes get this streaming or turbulent motion of the clouds caused by the prevailing winds moving around the elevated parts in the interior of the islands. It can be quite spectacular, with arrow shaped, herringbone shaped and en echelon clouds building up behind the island. You can also get a random turbulent motion as well, depending on how the wind blows across the island and the topography.
In this instance, it's almost as if this particular cloud is acting like a solid surface with some elevation, causing the prevailing winds in that particular belt to form eddy currents on the trailing end of the cloud. Those eddies are then acting as a site for cloud formation, probably by supercooling the flow of gas within each eddy (convective flow (uplift), releasing heat and cooling the gas).
