Secular solar flux variation

Figure 1

(see text)

Solar energy emission varies on all timescales right out to the change into a red dwarf, or so that particular theory goes.

A great deal of argument is ongoing as it has been from the mists of time on whether the sun is constant although today the sacrifice of goats or virgin daughters is less literal.

Today the matter of the solar constant remains. Related is TSI yet what exactly is meant and is it all there is and relevant?

In my view there is much more because the total extent of energy rather than direct radiation energy coupling is poorly known. Even the intensely studied thermal radiation (including “light” and radio) is still poorly defined. Space between the sun and earth might seem empty on an intensely sunny day but there is a fog of visible, magnetic, ionising and even particles.

And what about the geometry? The sun is very likely of variable size and so seems is the earth: as complete systems. The visible solar disc has in addition an “atmosphere” which radiates; the earth has layers too and these intercept or couple given magnetics.

During the 11 year sunspot cycle TSI varies about 0.1%. The solar system as a straightforward radiative system is ratiometric(1). The earth, sitting at a precise distance between the hot end and the cold end of deep space will change temperature exactly pro-rota, by 0.1% except for time constants. The earth has massive thermal inertia and cannot change other than glacially slowly. There is some evidence that the ethereal atmosphere which has essentially no inertia will respond fast. Perhaps this is the explanation for tropical storm variation but the data is poor (only reliable data avoiding spatial bias is satellite era).

(1) ratiometric is a term from electronics, where a system is purely multiplicative and exactly proportional such as a divider chain, reference at one end and zero at the other. A point between the two is at a distance. A famous example is the Whetstone bridge. Critically this works regardless of the details, doesn’t care what exactly merely that it is a ratio by some means.

I am citing two papers.

First a sit-on-the-fence which concludes with these wise words

‘‘The question whether the Sun’s apparent diameter is liable to periodic changes has frequently occupied the attention of the astronomers.’’ This was written in the Royal Astronomical Society Council report of 1875.
From the analysis of the available results today, this question remains totally up to date.”

However, my reading leaves the impression: that depends on the viewpoint, the research purpose of whether it is astronomy or physics. We do not even know the structure of the sun, just deductions and guesses. This goes right through to the neutron star theory of Oliver Manuel and contentious ideas. I don’t know, some seem potty and others are perfectly plausible.

Past, present and future measurements of the solar diameter
Gerard Thuilliera, Sabatino Sofiab, Margit Haberreiterc. 2005 (not sure of the correct citation)

Figure 2

ftp://ftp.pmodwrc.ch/pub/margit/papers/ThuillierSabHab2005ASpR.pdf

Representative of the views that the solar diameter does change and it matters is

LONG-TERM VARIATIONS OF THE INTEGRAL RADIATION FLUX AND
POSSIBLE TEMPERATURE CHANGES IN THE SOLAR CORE
Kh. I. Abdusamatov, 2005

Figure 3

http://www.gao.spb.ru/english/astrometr/KPhCB21_6_328.pdf

Headline image: SIDC ssn is bandpass filtered and the envelope of that computed via hilbert transform. The data ends need to be taken as uncertain.