From: Glenn Morton (glennmorton@entouch.net)
Date: Sun Nov 09 2003 - 14:31:25 EST
An item in this week's New Scientist caught my eye. It says:
"The sun is more active now than it has been for a millennium. The
realisation which comes from a reconstruction of sunspots stretching back
1150 years, comes just as the sun has thrown a minor tantrum. Last week, a
giant plume of material burst out from our star's surface and streamed into
space, sparking wrnings of an impending geomagnetic storm." Jenny HOgan,
"Hyperactive Sun Comes out in Spots," New Scientist, Nov. 1-7, 2003, p. 17
It made me do some searching through my radiative heat transfer files from
about 12 years ago because I recalled that there was a relationship between
sunspot number and solar output. I don't know what the thoughts are today
in that community about the relationship I recall, but here is what the
relationship is:
Irradiance = 1366.81 + 1366.81 * (0.078+0.0146 * Rz) Watts/m^2
Where Rz is the sunspot number. This is from Foukal and J. Lean, "An
Empirical Model of Total Solar Irradiance Variation Between 1874 and 1988,"
Science 247(1990):556-559. This article used satellite irradiance to do
their regression.
The thinking was similar in a 1992 article by Judith Lean, Andrew Skumanich
and Oran White, "Estimating the Sun's Radiative Output During the Maunder
Minimum," Geophysical REsearch Letters, 19(1992):15:1591-1594. They estimate
a .2% increase in solar radiation since the Maunder Minimum, a time in the
late 1600s and early 1700s when there was no sunspot cycle. During that time
(which was after the invention of the telescope) the appearance of a sunspot
was big news.
Frits-Christensen and Lassen, Science 254(1991):698-700 suggests that short
solar cycles correspond with higher activity and irradiance.
The New Scientist article concludes:
"The findings may stoke the controversy over the contribution of the sun to
global warming." Ibid. p. 17
I would think so. But then, I am about 10 years behind in this area.
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