Galactic Radiation at Radio Frequencies. VI. Low Altitude Scintillations of the Discrete Sources

Abstract

A study has been made of the scintillations of four discrete sources at altitudes of from 0 to 10°. The observations cover the years 1947?1951 and were made at various frequencies in the range 40?300 Mc/s. It was found that the scintillation index, a measure of the amplitude of the scintillations, (1) increases with increasing wavelength, (2) decreases rapidly with increasing altitude, (3) shows seasonal and diurnal variations, the seasonal component having minima near the equinoxes and the diurnal component near dawn and sunset. The scintillation rate or the number of scintillations per minute (1) is different for sources of different declination, (2) is independent of wavelength. In the case of the Cygnus source, the data for which are the most extensive, the rate increases and the decline in the scintillation index with altitude is less rapid during the winter months.