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Solar differential rotation reproduced with high-resolution simulation

Nature Astronomy volume 5, pages 1100–1102 (2021)Cite this article

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Abstract

The Sun rotates differentially with a fast equator and slow pole1. Convection in the solar interior is thought to maintain the differential rotation. However, although many numerical simulations have been conducted to reproduce the solar differential rotation2,3,4,5,6,7, previous high-resolution calculations with solar parameters fall into the antisolar (fast-pole) differential rotation regime. Consequently, we still do not know the true reason why the Sun has a fast-rotating equator. While the construction of the fast equator requires a strong rotational influence on the convection, the previous calculations have not been able to achieve the situation without any manipulations. The problem is called the convective conundrum8. The convection and the differential rotation in numerical simulations were different from the observations. Here, we show that a high-resolution calculation succeeds in reproducing the solar-like differential rotation. Our calculations indicate that the strong magnetic field generated by a small-scale dynamo has a significant impact on thermal convection. The successful reproduction of the differential rotation, convection and magnetic field achieved in our calculation is an essential step to understanding the cause of the most basic nature of solar activity, specifically, the 11 yr cycle of sunspot activity.

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Fig. 1: Overall structure of convection and magnetic field.
Fig. 2: Dependence of differential rotation on the resolution.
Fig. 3: Dependence of the convection and magnetic field properties on the resolution.
Fig. 4: Dependence of kinetic and magnetic energy spectra on the resolution.

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Data availability

The data generated, analysed and presented in this study are available at https://doi.org/10.5281/zenodo.5003258.

Code availability

We have opted not to make R2D2 code publicly available. Running R2D2 code requires expert assistance and an appropriate computer system. The numerical method is explained in our previous publications in detail5,18.

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Acknowledgements

We thank T. Yokoyama, R. Shimada and T. Hanawa for comments on the manuscript. The results were obtained using the supercomputer Fugaku provided by the RIKEN Center for Computational Science, the supercomputer Flow at Nagoya University and the Cray XC50 provided by the Center for Computational Astrophysics, National Astronomical Observatory of Japan. This work was supported by MEXT/JSPS KAKENHI (grants JP20K14510—principal investigator (PI) H.H., JP21H04492—PI K.K., JP21H01124—PI T. Yokoyama—and JP21H04497—PI H. Miayahara) and MEXT as a Program for Promoting Research on the Supercomputer Fugaku (Toward a unified view of the universe: from large-scale structures to planets, grant 20351188—PI J. Makino).

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Authors and Affiliations

  1. Department of Physics, Graduate School of Science, Chiba University, Chiba, Japan

    H. Hotta

  2. Institute for Space–Earth Environmental Research, Nagoya University, Nagoya, Japan

    K. Kusano

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  1. H. Hotta
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  2. K. Kusano
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Contributions

H.H. contributed to the design of the project, developed the numerical code, carried out simulations, performed analysis and wrote the first draft of the paper. K.K. contributed to the design of the project, interpretation of the result and writing of the final draft.

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Correspondence to H. Hotta.

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The authors declare no competing interests.

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Peer review information Nature Astronomy thanks Yuhong Fan, Juri Toomre and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–4 and Discussion.

Supplementary Video

Overall structure of convection and magnetic field. Left, right: the radial velocity and the radial magnetic field at r = 0.9R☉, respectively, where R☉ is the solar radius.

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Hotta, H., Kusano, K. Solar differential rotation reproduced with high-resolution simulation. Nat Astron 5, 1100–1102 (2021). https://doi.org/10.1038/s41550-021-01459-0

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