High-Resolution Studies of Ten Solar Active Regions at Wavelengths of 3-21 cm.

Abstract

view Abstract Citations (40) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS High-Resolution Studies of Ten Solar Active Regions at Wavelengths of 3-21 cm. Swarup, G. ; Kakinuma, T. ; Covington, A. E. ; Harvey, Gladys A. ; Mullaly, R. F. ; Rome, J. Abstract Pen strong sources of the slowly varying component (S-component) of solar radio emission have studied using high-resolution interferometers operating at wavelengths of 3 2, 7.5, 9 t, 10.7, and cm. All the ten radio sources were associated with sunspot groups having areas greater than about millionths of the solar hemisphere. The observations were obtained with interferometers which are ted at Nagoya, Ottawa, Stanford, and Sydney and which provide fan- and pencil-shaped beams ng widths of about 1-3 minutes of arc. This international co-operation has made it possible to study wavelength dependence of the S-component t appears that a strong source of the slowly varying component has a higher value of flux density 10 cm than at 3 cm or 21 cm. The size has a value of about 2-3 minutes of arc at wavelengths of d 10 cm and about 3 minutes of arc at 21 cm. The calculated values of heights show a large scatter are of the order of km at wavelengths of 3 and 10 cm, and about 40000-90000 km at :m. As other eclipse and interferometric observations have shown, the radio emission is circularly rized, with the degree of polarization being >30 per cent at 3 cm, 10 per cent at 10 cm, and < 2 per at 21 cm. At 10.7 cm, the brightness temperatures of the ten sources range from 1.6 to 3.8 X 100 K n it is assumed that the north-south widths of the sources are equal to the observed east-west widths. brightness temperatures show good correlation with both sunspot areas and magnetic fields. Phe above results about the flux-density spectrum and degree of polarization are not consistent with le magnetoionic theory, in which only the effect of electron-ion collisional absorption is considered. s been suggested that resonance absorption at harmonics of the gyromagnetic frequency should also onsidered to explain the above results (Kakinuma and Swarup 1962). The steadiness of the radio ,sion from a strong source over periods of days supports the hypothesis of the thermal origin. This lies that the electron temperature of the solar corona above a large sunspot group reaches values of er than 4 X 1000 K. However, the possibility that a part of the S-component arises non-thermally iot be ruled out at present. Publication: The Astrophysical Journal Pub Date: May 1963 DOI: 10.1086/147601 Bibcode: 1963ApJ...137.1251S full text sources ADS |