<abstract xmlns="http://www.w3.org/1999/xhtml">

Recent interest of solar physicists in the analysis of the coronal mass ejections and circular solar flares in fan-spine magnetic configurations (FSCs) necessitates measurements of the corresponding coronal magnetic fields. A dominant sunspot with the circumjacent magnetic flux of opposite polarity produces a specific coronal region of the quasi-transverse (QT-) propagation of microwaves. We make use of the theory of QT-propagation to evaluate the strengths of coronal magnetic fields in the active regions NOAA 11579, 12242, and 12488 while they are non-flaring. Microwave polarization changes were observed with the RATAN-600 radio telescope, the Siberian Solar Radio Telescope, and the Nobeyama Radioheliograph. Changes in the sign of circular radio polarization provide the strengths of coronal fields in a QT-region if the coronal plasma density <italic>N</italic>e and the length scale of magnetic field divergence <italic>L</italic>d are known. We evaluate the length scale by means of the potential-field source-surface (PFSS) model and the coronal density from the Gaussian inversion of the differential emission measure (from the Solar Dynamics Observatory observational data), obtaining <italic>N</italic>e <italic>L</italic>d = (0.46–0.64)×1010 m−2. The resulting coronal fields of 1.4×10−3 T and 2.34×10−3 T are attributed to the heights of 100 Mm and 50.2 Mm. We discuss the validity and consistency of the involved values to draw conclusions on the feasibility of coronal radio magnetography of FSCs.
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Recent interest of solar physicists in the analysis of the coronal mass ejections and circular solar flares in fan-spine magnetic configurations (FSCs) necessitates measurements of the corresponding coronal magnetic fields. A dominant sunspot with the circumjacent magnetic flux of opposite polarity produces a specific coronal region of the quasi-transverse (QT-) propagation of microwaves. We make use of the theory of QT-propagation to evaluate the strengths of coronal magnetic fields in the active regions NOAA 11579, 12242, and 12488 while they are non-flaring. Microwave polarization changes were observed with the RATAN-600 radio telescope, the Siberian Solar Radio Telescope, and the Nobeyama Radioheliograph. Changes in the sign of circular radio polarization provide the strengths of coronal fields in a QT-region if the coronal plasma density Ne and the length scale of magnetic field divergence Ld are known. We evaluate the length scale by means of the potential-field source-surface (PFSS) model and the coronal density from the Gaussian inversion of the differential emission measure (from the Solar Dynamics Observatory observational data), obtaining Ne Ld = (0.46–0.64)×1010 m−2. The resulting coronal fields of 1.4×10−3 T and 2.34×10−3 T are attributed to the heights of 100 Mm and 50.2 Mm. We discuss the validity and consistency of the involved values to draw conclusions on the feasibility of coronal radio magnetography of FSCs.

Radio Measurements of Coronal Magnetic Fields in Fan-Spine Configurations on the Sun

Latvian Journal of Physics and Technical Sciences

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Recent interest of solar physicists in the analysis of the coronal mass ejections and circular solar flares in fan-spine magnetic configurations (FSCs)...

Radio Measurements of Coronal Magnetic Fields in Fan-Spine Configurations on the Sun

Published Online: Apr 15, 2023

Page range: 52 - 62

DOI: https://doi.org/10.2478/lpts-2023-0011

Keywords
Solar magnetic field, solar microwave observations, Sun, sunspot

© 2023 B. Ryabov et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Radio Measurements of Coronal Magnetic Fields in Fan-Spine Configurations on the Sun

Published Online: Apr 15, 2023

Page range: 52 - 62

DOI: https://doi.org/10.2478/lpts-2023-0011

KeywordsSolar magnetic field, solar microwave observations, Sun, sunspot

© 2023 B. Ryabov et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
Solar magnetic field, solar microwave observations, Sun, sunspot