Magnetic Field Strengths and Structures from Radio Observations of Solar Active Regions

作     者：Chang－XiZhang G.B.Gelfreikh 等 Chang-Xi Zhang, G. B. Gelfreikh and Jing-Xiu Wang Department of Astronomy, Peking University, Beijing 100871 Chinese Academy of Science-Peking University Joint Beijing Astrophysics center, Beijing 100871 Pulkovo Astronomical Observatory, 196140 St. Peters

作者机构：DepartmentofAstronomyPekingUniversityBeijing100871 PulkovoAstronomicalObservatory196140St.PetersburgRussia 

出 版 物：《Chinese Journal of Astronomy and Astrophysics》 (中国天文和天体物理学报（英文版）)

年 卷 期：2002年第2卷第3期

页      面：266-276页

核心收录：

学科分类：07[理学] 070401[理学-天体物理] 0704[理学-天文学] 

主　　题：Sun: active regions   Sun: magnetic fields   Sun: optical observation   Sun: radio observation 

摘      要：Radio observations of some active regions (ARs) obtained with the Nobeyama radioheliograph at λ=1.76 cm are used for estimating the magnetic field strength in the upper chromosphere, based on thermal bremsstrahlung. The results are compared with the magnetic field strength in the photosphere from observations with the Solar Magnetic Field Telescope (SMFT) at Huairou Solar Observing Station of Beijing Astronomical Observatory. The difference in the magnetic field strength between the two layers seems reasonable. The solar radio maps of active regions obtained with the Nobeyama radioheliograph, both in total intensity (I-map) and in circular polarizations (V-map), are compared with the optical magnetograms obtained with the SMFT. The comparison between the radio map in circular polarization and the longitudinal photospheric magnetogram of a plage region suggests that the radio map in circular polarization is a kind of magnetogram of the upper chromosphere. The comparison of the radio map in total intensity with the photo-spheric vector magnetogram of an AR shows that the radio map in total intensity gives indications of magnetic loops in the corona, thus we have a method of defining the coronal magnetic structure from the radio I-maps at λ=1.76 cm. Analysing the I-maps, we identified three components: (a) a compact bright source; (b) a narrow elongated structure connecting two main magnetic islands of opposite polarities (observed in both the optical and radio magnetograms); (c) a wide, diffuse, weak component that corresponds to a wide structure in the solar active region which shows in most cases an S or a reversed S contour, which is probably due to the differential rotation of the Sun. The last two components suggest coronal loops on different spatial scales above the neutral line of the longitudinal photospheric magnetic field.