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Rotational shear in the low photosphere of the Sun

Published online by Cambridge University Press:  23 December 2024

T. Corbard Open the ORCID record for T. Corbard [Opens in a new window] ,
M. Faurobert ,
B. Gelly ,
R. Douet  and
D. Laforgue
T. Corbard*
Affiliation:
University Cote d’Azur, Cote d’Azur Observatory, CNRS UMR7293 J.L. Lagrange laboratory CNRS-IRL2009
M. Faurobert
Affiliation:
University Cote d’Azur, Cote d’Azur Observatory, CNRS UMR7293 J.L. Lagrange laboratory CNRS-IRL2009
B. Gelly
Affiliation:
University Cote d’Azur, Cote d’Azur Observatory, CNRS UMR7293 J.L. Lagrange laboratory CNRS-IRL2009
R. Douet
Affiliation:
University Cote d’Azur, Cote d’Azur Observatory, CNRS UMR7293 J.L. Lagrange laboratory CNRS-IRL2009
D. Laforgue
Affiliation:
University Cote d’Azur, Cote d’Azur Observatory, CNRS UMR7293 J.L. Lagrange laboratory CNRS-IRL2009
*
email: thierry.corbard@oca.eu
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Abstract

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We present a new method to measure the rotational height gradient in the solar photosphere. The method is inspired from differential interferometric techniques, we applied it to spectroscopic observations in the FeI 630.15 nm obtained at the solar telescope THEMIS which is equipped with an efficient adaptive optics system. The spectroscopic data was used to obtain images of the granulation at different line cords formed at different heights in the photosphere. Cross-correlation allows us to measure small systematic shifts between similar images. When observations are performed out of the center of the solar disk, the perspective effect gives rise to a radial shift between images formed at different heights. The measurement of this shift provides us with their formation-height difference. At the center of the disk the perspective effect vanishes but we measured a systematic retrograde shift along the east/west direction of the images formed at higher heights. The measured shifts are proportional to the formation height of the images. We interpret these findings as the evidence of a decrease of the rotational velocity with height in the low photosphere of the Sun and we give an estimate of this gradient.

Keywords

Sun: photospheredifferential rotationHigh angular resolution
Type
Contributed Paper
Information
Proceedings of the International Astronomical Union , Volume 19 , Symposium S365: Dynamics of Solar and Stellar Convection Zones and Atmospheres , December 2023 , pp. 48 - 53
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Copyright
© The Author(s), 2024. Published by Cambridge University Press on behalf of International Astronomical Union

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