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Earth motion, LoD and SORCE, mystery
I have unexpected results to do with LoD (Length of Day) Earth LoD does have a significant earth oribital factor but it does not amplitude or phase match earth distance. Present this first as pictures.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
| - | TSI | LoD |
|---|---|---|
| ratio | 47.98 | 1.13 |
Figure 6
Figure 6, confirmation of ratio of fundamental to second harmonic via transform.
Something completely unexpected has turned up during data preparation to do with helping someone elsewhere. Perhaps I simply didn’t know about this in which case can someone explain why this result is so? I would appreciate a sanity check in case I have made a mistake.
I was working on LoD (Length of [Earth] Day) daily data, specifically looking at the 1 year and 0.5 year characteristic, which is to do with the orbit around the sun. Although slightly elliptical it is very closely approximated by a Fourier pair, 1y fundamental and 0.5y second harmonic. On using software here to lock to and subtract out this signal, something I do often with data and have done on this dataset before, I noticed it didn’t look right.
Been busy on personal matters. On coming back to the problem I decided to do a compare with earth orbital distance to get the relative phase and ratio of amplitudes. An obvious source of data is SORCE TSI at earth distance. (which I already know) SORCE data of course shows closet approach 4th January. And LoD?
This result is so strange a careful sanity check is needed. I’ve reworked using a common time frame instead of the fancy referencing I tend to do. (completely valid anyway, turns out it doesn’t make the slightest difference)
Reworked, SORCE data commences 20030225.5, 25th February 2003 at 12 hours. Data is common to 15th May 2012, end of LoD dataset.
Data
SORCE using full mission daily. Data column 10.
LoD l’Observatoire of Paris (same data as iers site), take link “Celestial Pole offsets (dX,dY) referred to the precession-nutation model IAU 2000″ which produces a text file of daily data 1962 onwards. Data column labelled oddly enough LoD.
Large XLS of data used and working models. (literally used to do the plots etc.) The model phase and amplitudes can be taken as accurate. Phase is relative to data start date.
Post by Tim Channon
(note, might comment little, I still have serious computer problems here, still have to find a fix for backup drive / software failure)
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