Sunday Feb 5 2012 - Dust
In New Orleans, a few questions recurred. One: what about dust; two: what about above the atmosphere measurements of these shadows. So I am trying to set out these issues: dust and top of the atmosphere measurement of solar irradiance.
As to dust, there is a recent report published by the National Academies Press that describes the space dust environment.
http://www.nap.edu/catalog.php?record_id=4765.
It indicates as I understand that the space program has a good estimate on dust down to 2 mm, within 1000 km of the earth's surface, and of 10 mm and less, out to GEO or so. That's all we are sort of sure of. But I'm studying the report today to be sure of this. But let us compare that capacity to the size of particles in dust storms. Here is an Iraqi study of that:
http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel4%2F8%2F76%2F00001082.pdf%3Farnumber%3D1082&authDecision=-203
It seems 2-3ยตm is the mode of the distribution. So 2 mm is way big. The same article also measures the attenuation due to the dust storms. Not completely sure I want to use the attenuation due to however much survived atmospheric passage - though by the same token, if not, I am saying the distribution in space may be different- though again, surely it is the bigger particles that would survive and the dust in space would not be yet smaller? Well I may consider their attenuation numbers as relevant. In any case here is an Iraqi sandstorm:
http://www.sunbelt-software.com/stu/iraq/sandstorm.htm
Apropos of that, am also trying to keep track of the statistics on dust storms, on the notion that this is what the rings become when they fall to earth. It is just a playing around idea at the moment. But so I see that there were freak storms Feb 5-6, 2008, in a swathe of the US. Well, the usual Moon Ring swathe is too far out to cause that, so I wondered what if it were a near-in ringlet, at a bit of a tilt, as it might easily be considering how "tall" Saturn's Phoebe ring is. But if it were so close in, then it should have crashed, so I checked for dust storms, and sure enough here is one March 4 2008:
http://earthobservatory.nasa.gov/IOTD/view.php?id=8477
At the same site I noticed that dust storms have become much more common recently in China. They are attributed to industrialization etc. but as is noted in other contexts, people tend to explain puzzling changes in terms of some nearby possible cause. Hal's book says (check this) that tektites have the same chemical composition as loess. I think the point people were making there is that tektites could be terrestrial but the point certainly cuts both ways. I note they are saying the dust storms are toxic. I wonder with what?
