The Astrophysical Journal Letters recently published research results achieved by the staff of Fuxian Solar Observatory, Yunnan Observatories. They found that the quiet solar chromosphere rotates faster than the photosphere below it, which is the evidence for the heating of the solar quiet chromosphere by small-scale magnetic activities.

Differential rotation is an important feature of the sun and other stars, which plays an important role in understanding the role of dynamo and magnetic field. Researchers analyzed synthetic maps of He I intensity. They also studied the differential rotation of the solar chromosphere observed by He I absorption line.

Surprisingly, the chromosphere is found to rotate faster than the photosphere beneath it. The anomalous heating of the chromosphere and corona has been a major problem in modern astronomy.

By studying the rotation properties of the quiet chromosphere, they speculate that, it is the small-scale magnetic elements with magnetic flux in the range of (2.9–32.0)×1018 Mx which are anchored in the leptocline, that heat the quiet chromosphere to present the anomalous temperature increase, causing it to rotate at the same rate as the leptocline; and thus the leptocline, the quiet chromosphere, and the magnetic elements are all in anti-phase with the solar cycle.

In the photosphere, the strong magnetic fields are known to suppress the differential of rotation rate, in contrast in the chromosphere, the strong magnetic fields are found to enhance the differential of rotation rate. Furthermore, they addressed some issues on differential rotation: why does the solar atmosphere rotate faster in upper layer than in lower layer? why is the rotation rate determined by small-scale magnetic fields larger than that determined by large-scale magnetic fields, why do they both rotate faster than the photosphere plasma? why do the strong magnetic fields suppress the differential of rotation rate in the photosphere but strengthen in the chromosphere? how does the torsional oscillation form? and so on.

Contact:

LI Kejun,Yunnan Observatories, CAS

lkj@ynao.ac.cn