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| Titel |
Solution to the discrepancy between the seismic and photospheric solar radius |
| VerfasserIn |
M. Haberreiter, A. G. Kosovichev, W. Schmutz |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022474
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| Zusammenfassung |
| Two methods are usually used to observationally determine the solar radius: One
is the observation of the intensity profile at the limb, the other one uses f-mode
frequencies to derive a ’seismic’ solar radius which is then corrected to optical
depth unity. The two methods are inconsistent and lead to a difference in the solar
radius of approx. 0.3 Mm. Based on radiative transfer calculations we show that this
discrepancy can be explained by the difference between the height at disk center
where tau500=1 and the inflection point of the intensity profile on the limb. We
calculate the intensity profile of the limb for the MDI continuum and the continuum at
5000 A for two atmosphere structures and compare the position of the inflection
points with the radius at optical depth unity. The calculated difference between the
’seismic’ radius and the inflection point is 0.347 Mm with respect to optical depth unity
and 0.333 Mm with respect to the Rossland mean opacity. We conclude that the
standard solar radius in evolutionary models has to be lowered by 0.333 Mm and
is 695.66 Mm. This correction reconciles inflection point measurements and the
seismic radius within the uncertainty. This finding is very important for the analysis
of the solar diameter measurements with the SODISM instrument on PICARD. |
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