Rotation is a significant characteristic of the Sun and other stars, and it plays an important role in understanding their dynamo actions and magnetic activities. In this study, the rotation of the solar chromospheric activity is investigated from a global point of view with an over 40 yr Mg II index. We determined the time-varying rotational period lengths (RPLs) with the synchrosqueezed wavelet transform which provides high temporal and frequency resolution; furthermore, we compared the RPLs with the photospheric and coronal RPLs obtained from the sunspot numbers and the 10.7 cm radio flux data. The significance of the RPLs is taken into consideration. We found that the RPLs of the chromosphere exhibit a downward trend, as do those that of the photosphere and corona; in addition, their RPLs at the recent four solar maxima also show a declining trend. It suggests that the rotation of the solar atmosphere has been accelerating during the recent four solar cycles, which is inferred to be caused by the declining strength of solar activity. The variations of the solar atmospheric RPLs show periodicities of multiple harmonics of the solar cycle period, and it is modulated by the solar activity cycle.

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关于太阳色层的自转

自转是太阳和其他恒星的一个重要特征，它在理解它们的发电机作用和磁活动方面起着重要作用。在这项研究中，太阳色球活动的旋转是从全球角度研究的，具有超过 40 年的 Mg II 指数。我们使用同步压缩小波变换确定了时变旋转周期长度 (RPL)，该变换提供了高时间和频率分辨率；此外，我们将 RPL 与从太阳黑子数和 10.7 cm 无线电通量数据获得的光球层和日冕 RPL 进行了比较。考虑了 RPL 的重要性。我们发现色球的 RPL 呈现下降趋势，光球和日冕的 RPL 也是如此；此外，他们在最近四个太阳极大值的 RPL 也呈现下降趋势。这表明在最近的四个太阳周期中太阳大气的旋转一直在加速，推测这是由于太阳活动强度下降造成的。太阳大气 RPL 的变化表现出太阳活动周期多次谐波的周期性，并受太阳活动周期的调制。