Measurements of Solar Radiation at a Wavelength of 50 Centimetres during the Eclipse of November 1, 1948

Abstract

Radio-frequency power received from the sun at a wavelength of 50 cm. was measured at three well-separated places during the solar eclipse of November 1, 1948. Abrupt changes in slope on the records of received flux density were interpreted as being the result of the covering and uncovering on the sun of small areas of great radio brightness. These areas were found to be associated with some visible sunspots, with positions previously occupied by sunspots, and with one prominence. The average effective temperature of the bright areas was about 5 X 10⁶ °K., and the are= contributed a total power of roughly one-fifth of that from the entire sun. After the effects of active areas had been taken into account, the remaining four- fifths of the power received from the sun was found to originate from a source larger than the visible disk. About 40 per cent. of the power from this source originated outside the edge of the visible disk. The results were consistent with a theoretical distribution of brightness on the source, which involved limb-brightening. The relative magnitudes of the two circularly-polarized components of the solar radiation showed small differences as the bright areas were eclipsed. No predominance of one component was seen when one hemisphere of the sun was eclipsed ; hence no effects of any general magnetic field on the sun were detected.