Reduced Microwave Brightness Temperature in a Sunspot Atmosphere Due to Open Magnetic Fields

Motivated by dark coronal lanes in 284 Å extreme-ultraviolet (EUV) observations from the Extreme-ultraviolet Imaging Telescope on board the Solar and Heliospheric Observatory (SOHO/EIT), we construct and optimize an atmosphere model of the active region (AR) 8535 sunspot by adding a cool and dense c...

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Bibliographic Details
Published in:Solar physics 2021-10, Vol.296 (10), Article 144
Main Authors: Vrublevskis, A., Ryabov, B. I., White, S. M.
Format: Article
Language:English
Subjects:
Astrophysics and Astroparticles
Atmosphere
Atmospheric models
Atmospheric Sciences
Brightness temperature
Investigations
Magnetic fields
Observatories
Physics
Physics and Astronomy
Plasma
Plasma temperature
Radiation
Soft x rays
SOHO Mission
Solar physics
Solar wind
Solar wind sources
Space Exploration and Astronautics
Space Sciences (including Extraterrestrial Physics
Sunspots
Temperature
X-rays
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Summary:Motivated by dark coronal lanes in 284 Å extreme-ultraviolet (EUV) observations from the Extreme-ultraviolet Imaging Telescope on board the Solar and Heliospheric Observatory (SOHO/EIT), we construct and optimize an atmosphere model of the active region (AR) 8535 sunspot by adding a cool and dense component in the volume of plasma along open field lines determined using the potential-field source-surface (PFSS) extrapolation. Our model qualitatively reproduces the observed reduced microwave brightness temperature in the northern part of the sunspot in Very Large Array (VLA) observations from 13 May 1999 and provides a physical explanation for the coronal dark lanes. We propose the application of this method to other sunspots with such observed dark regions in the EUV or soft X-rays and with concurrent microwave observations to determine the significance of open field regions. The connection between open fields and the resulting plasma temperature and density change is of relevance for slow solar wind source investigations.
ISSN:0038-0938
1573-093X
DOI:10.1007/s11207-021-01891-5