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Re: PERIHELION etc.

Chuck wrote

-----Original Message-----
From: Chuck Britton [mailto:britton@NCSSM.EDU]
Sent: Sunday, January 04, 2004 12:57 PM

Today (Jan. 4) we are celebrating the annual perihelion.

The distance to the sun is about 3 % less than at the aphelion.

This makes the solar radiation about 10 % larger - right?!

More like 6% - but the angle is more oblique for us in the northern hemisphere, so the flux per unit surface area also goes like cosine of the sun's angular distance from zenith. For my location, in the summertime the Sun reaches about 15 degrees from zenith. Assuming the summer flux is 1 unit, this gives about cos(15 degrees) ~ .97 "flux units". Today, the minimum zenith angle is more like 60 degrees. So the surface flux is more like .94 cos(60 degrees) ~ .47 flux units.

********************************************
"I am greatly relieved that the universe
is finally explainable. I was beginning to
think it was me." - Woody Allen
********************************************
George Spagna
Department of Physics
Randolph-Macon College
P.O. Box 5005
Ashland, VA 23005-5505
phone: (804) 752-7344
FAX (804) 752-4724
e-mail: gspagna@rmc.edu
http://faculty.rmc.edu/gspagna