NJU scientists paints a picture of the Sun! China's first solar explorer "Xihe" makes a new discovery!

In June 2024, researchers from Nanjing University, Yunnan Observatories of the Chinese Academy of Sciences, and Shanghai Institute of Satellite Engineering analyzed observational data from China's first solar explorer "Xihe," and accurately created the world's first three-dimensional image of the solar atmosphere's rotation. They found that the solar atmosphere rotates gradually faster from the lower to upper layers. Such an abnormal rotation has important implications to the solar dynamo, atmospheric structure and evolution.

These results were published in the journal of Nature Astronomy on June 13, 2024 (, which is entitled “Height-dependent differential rotation of the solar atmosphere detected by CHASE.” The first author is Shihao Rao, a doctoral student at the School of Astronomy and Space Science, Nanjing University. The corresponding authors are Prof. Chuan Li and Prof. Mingde Ding. Prof. Cheng Fang, Academician of CAS, provided important advice.

The abstract of the paper is as following:

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 (6,560.58 Å), Hα (6,562.81 Å) and Fe I (6,569.21 Å) with a spectral resolution of 0.024 Å. We find that the Sun rotates progressively faster from the photosphere to the chromosphere. For example, at the equator, it increases from 2.81 ± 0.02 μrad s−1 at the bottom of the photosphere to 3.08 ± 0.05 μrad s−1 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.

Link to the paper:

Source: School of Astronomy and Space Science

Correspondent: Li Chuan, Ding Mingde