Abstract
Rotation is an intrinsic property of stars and provides essential constraints on their structure, formation, evolution and interaction with the interplanetary environment. The Sun provides a unique opportunity to explore stellar rotation from the interior to its atmosphere in great detail. We know that the Sun rotates faster at the equator than at the poles, but how this differential rotation behaves at different atmospheric layers within it is not yet clear. Here we extract the rotation curves of different layers of the solar photosphere and chromosphere by using whole-disk Dopplergrams obtained by the Chinese Hα Solar Explorer (CHASE) for the wavebands Si i (6,560.58âà ), Hα (6,562.81âà ) and Fe i (6,569.21âà ) with a spectral resolution of 0.024âà . We find that the Sun rotates progressively faster from the photosphere to the chromosphere. For example, at the equator, it increases from 2.81â±â0.02âμradâsâ1 at the bottom of the photosphere to 3.08â±â0.05âμradâsâ1 in the chromosphere. The ubiquitous small-scale magnetic fields and the height-dependent degree of their frozen-in effect with the solar atmosphere are plausible causes of the height-dependent rotation rate. The results have important implications for understanding solar subsurface processes and solar atmospheric dynamics.
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Data availability
The CHASE data are available from the Solar Science Data Center of Nanjing University (https://ssdc.nju.edu.cn). The specific data applied in this study are stored at a separate link: https://sdc.nju.edu.cn/d/90242dc5043d46b1b140. The SDO/HMI data can be accessed from the Joint Science Operations Center (http://jsoc.stanford.edu).
Code availability
The codes used to read CHASE data and derive Doppler velocities are available from the Solar Science Data Center (https://ssdc.nju.edu.cn/NdchaseSatellite).
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Acknowledgements
This work uses data from the CHASE mission supported by the China National Space Administration. Magnetic field data were provided courtesy of the SDO and HMI science team. C.L. is supported by the National Natural Science Foundation of China (NSFC; Grant No. 12333009) and the China National Space Administration (Project No. 050101). M.D.D. is supported by the NSFC (Grant No. 12127901). F.C. is supported by the NSFC (Grant No. 12373054) and the Programme for Innovative Talents and Entrepreneurs of Jiangsu Province. P.F.C. is supported by the National Key R&D Program of China (Grant No. 2020YFC2201200). K.J.L. is supported by the NSFC (Grant No. 12373059) and the Basic Research Foundation of Yunnan Province (Grant No. 202201AS070042). Q.H. is supported by the NSFC (Grant No. 12173019). Y.G. is supported by the National Key R&D Program of China (Grant No. 2022YFF0503004). We thank J. Jiang for fruitful discussions.
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C.L. and C.F. proposed this study and the data analysis method. M.D.D. is the chief scientist of the CHASE mission and responsible for the scientific interpretation of this project. S.H.R. analysed all the observational data. J.H. calculated the formation heights of the spectral lines. F.C. and K.J.L. contributed to the interpretation of the results. Y.Q. and Z.L. contributed to the calibration procedures of the CHASE data. S.H.R., C.L. and M.D.D. wrote the manuscript. All authors joined the discussions and commented on the results.
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Extended data
Extended Data Fig. 1 A sample of Dopplegrams derived from a series of scanning sequences on 5 December 2021.
The corresponding differential rotation curves of different solar surface layers are shown in the right column.
Extended Data Fig. 2 A sample of Dopplegrams derived from a series of scanning sequences on 7 December 2021.
The corresponding differential rotation curves of different solar surface layers are shown in the right column.
Extended Data Fig. 3 The distribution of uncertainties of the angular velocities shown in Fig. 2.
The uncertainties of the angular velocities are calculated from the uncertainties of the rotation parameters listed in Table 1 by using the error propagation formula. A cubic spline interpolation is used between discrete altitudes when plotting the distribution map.
Extended Data Fig. 4 Comparison of the intrinsic velocity field in the photosphere with the line-of-sight magnetogram.
The intrinsic velocity field is obtained from the Dopplergram of Fig. 1(b) with subtraction of the differential rotation. The contours of upflows and downflows in the zoom-in regions are overlaid on the magnetograms of SDO/HMI.
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Supplementary Fig. 1.
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Rao, S., Li, C., Ding, M. et al. Height-dependent differential rotation of the solar atmosphere detected by CHASE. Nat Astron 8, 1102â1109 (2024). https://doi.org/10.1038/s41550-024-02299-4
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DOI: https://doi.org/10.1038/s41550-024-02299-4