Measurement of magnetic fields in the solar atmosphere above sun spots using gyroresonance emission

• Published in: Solar physics 1982-01, Vol.79 (1), p.41-58
• Main Author: Akhmedov, S B
• Format: Article
• Language: English
• ISSN: 0038-0938

An analysis of the local sources (LS) structure of the S-component of solar radio emission confirms the presence of a core component that is characterized by strong circular polarization and a steep growing spectrum at shorter centimeter wavelengths. These details coincide in position with the sun-spots' umbra, and their height above the photosphere does not generally exceed similar to 2000 km. Gyroresonance emission of thermal electrons of the corona is generally accepted as being responsible for this type of emission. The spectral and polarization observations of LS made with RATAN-600 by using high resolution in the wavelength range 2.0-4.0 cm, make it possible to measure the maximum magnetic fields of the corresponding sun spots at the height of the chromosphere-corona transition region (CCTR). This method is based upon the determination of the short-wavelength limit of gyroresonance emission of the LS and its relation to the third harmonic of gyrofrequency. An analysis of a large number of sun spots and their LS (core component) has shown a good correlation between radio magnetic fields near the CCTR and optical photospheric ones. The magnetic field in CCTR above a sun spot is found only 10-20% lower than in the photosphere. The resulting gradient of the field strength is not less than 0.25 G km super(-) super(1) . This result seems to contradict the lower values of magnetic fields generally found above sun spots using the chromospheric H alpha line. Some possible ways of overcoming this difficulty are proposed.