Solar Radiation at 1200 MC/S., 600 MC/S., and 200 MC/S

Abstract

Daily observations of solar radiation at frequencies of 1200 Mc/s., 600 Mc/s., and 200 Mc/s. taken between August 18 and November 30, 1947, are described. The characteristics of the radiation at 200 Mc/s. were in general agreement with those observed by earlier workers. At 600 Mc/s. and 1200 Mc/s., the received intensity was normally steady on any one day but underwent long-period variations over a range of about two to one. The radiation received when the sun was almost free of sunspots corresponded to an effective black-body temperature of 0.5 million �K. at 600 Mc/s. and 0.1 million �K. at 1200 Mc/s. As sunspots appeared, the temperature rose and showed marked oar- relation with sunspot area. It is considered that radiation at these frequencies is entirely thermal in origin and that the long-period variations are at least partly due to the influence of the magnetic field of sunspots on the mechanism of thermal emission from a magneto-ionic medium. On a few occasions, isolated disturbances were observed on 600 Mc/s. and 1200 Mc/s. some of which were associated with chromospheric flares and radio fade-outs. The difficulties arising in the calibration of the apparatus and the steps taken to overcome them are discussed in detail.

The 10.7 cm solar radio flux (F10.7)

“…When a series of calibrated measurements were made over many days, two things emerged: the measured flux measurements corresponded to disk brightness temperatures much larger than 6000 K (the temperature of the photosphere), and equally surprisingly, the solar flux densities at this wavelength varied from day to day. The connection between sunspots and solar centimetric emissions was discovered independently by Covington [, ], Lehaney and Yabsley [], and through a statistical study, Denisse []. Covington [] used the edge of the Moon during a solar eclipse to identify a significant emission contribution associated with a large active region.…”

Harmonic Analysis of Time Variations Observed in the Solar Radio Flux Measured at 810 MHz from 1957 to 2004

“…The SVC was first discovered by Covington (1947Covington ( , 1948 at 10.7 cm, and by Lehany & Yabsley (1949) at 25 and 50 cm. At different wavelengths in the 1-100 cm range, various emission mechanisms are responsible for contributions to the SVC.…”

Fine-Scale Radio Studies of the Sun.

“…It soon became apparent, however, that the observations which have been used in support of these models could have led to " misleading conclusions, for the unresolved "cores" could be associated with either sunspots or bright plage, the polarization measurements could be affected by beam dilution effects, and the observed circular polarization could be accounted for by propagation effects without an appeal to gyroresonant absorption (Covington, 1949;Lehany and Yabsley, 1949;Denisse, 1950;Gelfreich et al, 1959).…”