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Geometrical information on the solar shape: high precision results with SDO/HMI

Published online by Cambridge University Press:  18 July 2013

Xiaofan Wang  and
Costantino Sigismondi
Xiaofan Wang
Affiliation:
Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, email: wxf@nao.cas.cn
Costantino Sigismondi
Affiliation:
ICRA/Sapienza Università di Roma, Ateneo Pontificio Regina Apostolorum, email: sigismondi@icra.it
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Abstract

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The uncertainty of measurement of solar diameter is depending on the observational time scale. Full-disc images of SDO/HMI and the images from ground observations in Huairou Solar Observing Station have been analyzed to get the values of solar diameter. The satellite observations reach a very high precision, but the absolute image scale still need to be calibrated. The solar oblateness is a more challenging measurement than the diameter, since the signal amplitude is a few milli-arcseconds. It is a relative measurement, then not affected by the pixel scale calibration required by the diameter measurement. But the results are strongly dependent on the state of instrument such as focus plane deformation and on the calculation process.

Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 8 , Symposium S294: Solar and Astrophysical Dynamos and Magnetic Activity , August 2012 , pp. 483 - 484
Copyright
Copyright © International Astronomical Union 2013 

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