Dr. XIANG Nanbin from Yunnan Observatories of the Chinese Academy of Sciences (CAS), in collaboration with Researcher ZHAO Xinhua from State Key Laboratory of Space Weather at National Space Science Center of the CAS, and Professor DENG Linhua from Yunnan Minzu University, has made progress in studying the radial differential rotation of solar corona.

This study was published in The Astrophysical Journal, providing new insights into the regularity of coronal rotation varying with altitude and its temporal evolution.

The solar corona exhibits differential rotation in both radial and latitudinal directions. This complex rotation facilitates magnetic reconnection in the solar corona, releasing the free energy stored in the magnetic field due to the shearing and twisting motions from varying surface rotation rates. Understanding this process is crucial for unraveling coronal dynamics and heating mechanisms.

However, studying coronal rotation is challenging due to the optical thinness of the corona in extreme ultraviolet radiation and the absence of long-lived solar structures that can serve as rotational tracers. Consequently, the variation of coronal rotation with altitude remains poorly understood.

Solar physicists have believed that solar radio emissions at different frequencies originate from varying altitudes in the upper solar atmosphere. Building on this understanding, the researchers conducted an in-depth study of the radial differential rotation of the solar corona and its temporal variation patterns. Using daily full-disk solar noon radio flux data from the Radio Solar Telescope Network (245-8800 MHz), they found that over the past 30 years, the rotation rate of solar radio flux increased with frequency, confirming the existence of radial differential rotation in the solar corona across three solar cycles.

Furthermore, the researchers also revealed altitude-dependent variations in the rotation of the upper solar atmosphere. From the temporal evolution of the rotation period lengths of solar radio flux, the coronal rotation at altitudes from the low corona to approximately 1.3 solar radii exhibited complex variations as the solar activity cycle progressed. However, the coronal rotation rate within this altitude range has consistently slowed down gradually with increasing altitude over the past three decades.

This study enhances the understanding of upper solar atmospheric rotation, and provides critical insights into coronal dynamics and abnormal heating.

This study was supported by multiple funding sources, including the National Natural Science Foundation of China, the Strategic Priority Research Program of the CAS, Yunnan Revitalization Talent Support Program, and other regional and national initiatives.