Science has an international nature and, in many problems, significant progress can be achieved through close cooperation between scientists from different countries. Solar physics, which is becoming more and more practically important (e.g. in the context of space weather issues) is not an exception. Many international scientific groups have been working on the different topics, trying to understand the active processes at work in our nearest star. Since the main sources of solar instability are different manifestations of solar magnetic fields, many efforts of the solar physics community have been devoted to the observation and analysis of such fields.

As a part of long-term scientific cooperation between Russia and China, the joint projects between the Institute of Solar-Terrestrial Physics (Irkutsk) and the Key Laboratory of Solar Activity of the Chinese Academy of Sciences (CAS) (Beijing) have received powerful support in terms of Russian-Chinese conferences on space weather. After one of such conference which was held in Russia, all participants were invited to the Chinese Consulate-General in Irkutsk. Among other partners from the Chinese side, some solar physicists attended this meeting.

The other reason for fruitful Chinese-Russian cooperation, besides the close geographical positions of Irkutsk and Beijing, is a common scientific interest in exploration of global solar magnetism. Only in Irkutsk in Russia and at the Huairou Solar Observing Station (HSOS) in China are there instrumental facilities for the observation of full-disk solar magnetograms. This is the STOP (Solar Telescope for Operative Predictions) telescope at Sayan observatory and SMAT (Solar Magnetism and Activity Telescope) at HSOS. This fact provides a good basis for the organization of coordinated measurements using the two instruments and for their joint analysis.

As a logical result of this motivation, a joint Chinese-Russian proposal for the CAS President’s International Fellowship Initiative (PIFI) was suggested at the end of 2016 and approved at the beginning of 2017. The title of the proposal is “Cross-Comparison of Full-Disk Solar Magnetic Fields Measurements Obtained with Chinese, Russian and Other Observatories: Instrumental and Solar Physics Issues”.

In the context of this PIFI project, Demidov M.L. has made three very useful and interesting visits to China. Most of the time he has spent at HSOS, participating in routine observations run together with HSOS staff, making some original experiments, etc. The main partner of all experiments on the SMAT telescope, which were devoted to the study of its numerous polarization effects, was Professor Wang Xiaofan. Due to help from Professor Wang it was possible to undertake many experiments which finally helped us to understand the main reasons of SMAT problems in observations of magnetic fields distributions across the solar disk. In this case a special optical element (half-wave phase plate) was installed in front of the telescope’s objective.

Many efforts have been made in the processing of SMAT observations, and comparison of them with STOP and other instruments’ [mainly with SDO/HMI and IRmag (NAOJ, Mitaka, Japan) magnetograms] data sets. A conclusion about the necessity of observations at SMAT in two wings of spectral line was made. Observations only in one wing can provide more or less reliable data only in the case of observations with a small entrance aperture.

There is no doubt that cooperation between the Russian Institute of Solar-Terrestrial Physics SB RAS and the Chinese Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, has been very fruitful in the past and there are good prospects for future collaboration as well.

Source: National Astronomical Observatories,

Chinese Academy of Sciences