National Astronomical Observatories, Chinese Academy of Sciences
Irkutsk, Russian Federation
State Key Laboratory of Solar Activity and Space Weather, National Space Science Center, Chinese Academy of Sciences
Beijing, China
State Key Laboratory of Solar Activity and Space Weather, National Space Science Center, Chinese Academy of Sciences
Beijing, China
State Key Laboratory of Solar Activity and Space Weather, National Space Science Center, Chinese Academy of Sciences
School of Astronomy and Space Science, University of Chinese Academy of Sciences
Beijing, China
One of the very important international events in space science that has happened recently is the launch of the International Meridian Circle Program (IMCP). A key element of IMCP is a quite new instrument — the Solar Full-disk Multi-layer Magnetograph (SFMM) installed at Gan Yu Solar Station (GYSS) of the Purple Mountain Observatory (Jiangsu Province). The main objective of this telescope is to provide data on distribution of magnetic fields across the solar surface, which is necessary for prediction of some space weather (SW) parameters since this information is actually the low boundary condition for corresponding numerical simulations. There are plans to construct a network of such telescopes (similar to GONG or to ngGONG), so it is very important to test how reliable the measurements of weak large-scale magnetic fields (LSMF) are with these instruments. It is just LSMF, not strong magnetic fields in active regions (which are relatively easy to measure), that determines the structure of the heliosphere. To do this, using first observations with SFMM at GYSS, is the main purpose of this study. After a brief description of the instrument and some methodical issues, we present the results of comparison of SFMM observations with the Wilcox Solar Observatory (WSO) data. WSO measurements of LSMF are the most reliable in the world, and the results of such comparison are extremely important. We have found out that the correlation coefficient is high enough (≈0.70) if we consider the whole range of measured strengths, but it is lower (≈0.57) if the consideration is rerstricted only to relatively weak (|B|≤10.0 G) fields. Note that there is a significant difference between regression coefficients (R) for these two cases: R≈5.1 in first case and only R≈1.8 in the second one. The reason of this is still unclear and will be the subject of future investigations.
the Sun, solar magnetic field, space weather, telescope
1. Chen J., Su J., Xie W., Deng Y., Bai X., et al. Direct measurement of the longitudinal magnetic field in the solar photosphere with the Zeeman effect. Solar Phys. 2025, vol. 300, iss. 4, article id. 49. DOI:https://doi.org/10.10007/s11207-025-02455-7.
2. Demidov M.L., Wang X.F., Wang D.G., Deng, Y.Y. On the measurements of full-disk longitudinal magnetograms at Huairou solar observing station. Solar Phys. 2018, vol. 293, iss. 10, article id. 146, 18 p. DOI:https://doi.org/10.10007/s11207-018-1366-6.
3. Demidov M.L., Hanaoka Y., Wang X.F., Kirichkov P.N. On the differences in the ambient solar wind speed forecasting caused by using synoptic maps from different observatories. Solar Phys. 2023, vol. 298, article id. 120, 14 p. DOI:https://doi.org/10.10007/s11207-023-02206-6.
4. Linker J.A., Caplan R.M., Downs C., P. Riley, Z. Mikic, et al. The open flux problem. Astroph. J. 2017, vol. 848, no. 1, 11 p. DOI:https://doi.org/10.3847/1538-4357/aa8a70.
5. Sun Y., Tong L., Deng Y., Wang D., Wang X., et al. Development of the full-disk vector magnetographs for the Meridian Project II. The 15th Russian-Chinese Workshop on Space Weather. Irkutsk. Russia, 2024, p. 46.
6. Uitenbroek H. The accuracy of the center-of-gravity method for measuring velocity and magnetic field strength in the solar photosphere. Astrophys. J. 2003, vol. 592. p. 1225–1233. DOI:https://doi.org/10.1086/375736.
7. Wang Y.-M., Ulrich R.K., Harvey J.W. Magnetograph saturation and open flux problem. Astroph. J. 2022, vol. 926, article id. 113, 14 p. DOI:https://doi.org/10.3847/1538-4357/ac4491.
8. Xu H., Su J., Liu S., et al. Comparison of line-of-sight magnetic field observed by ASO-S/FMG, SDO/HMI and HSOS/SMAT. Solar Phys. 2024, vol. 299, article id. 17. DOI:https://doi.org/10.1007/s11207-024-02260-8.
9. URL: http://wso.stanford.edu (accessed April 23, 2025).
