Accession Number : AD0614161

Title :   IONOSPHERIC AND TROPOSPHERIC SCINTILLATIONS OF A RADIO STAR AT ZERO TO FIVE DEGREES OF ELEVATION.

Descriptive Note : Environmental research papers,

Corporate Author : AIR FORCE CAMBRIDGE RESEARCH LABS L G HANSCOM FIELD MASS

Personal Author(s) : Castelli,John P. ; Aarons,Jules ; silverman,Herbert M.

Report Date : 06 JUN 1964

Pagination or Media Count : 26

Abstract : Using Cygnus A as the source, a multi-frequency study of both scintillation rate and index was made in 1961 and 1962. Using an 84 ft parabola, simultaneous observations were made at 63, 112, 225, 1200, and 2980 Mc/s with angles of elevation from 0 to 5 degrees. Tropospheric scintillation rates at 1200 and 2980 Mc/s increase as the angle of elevation increased; the mean scintillation rates rose from 1x00/min at 1 degree of elevation to 1x75/min at 3 degrees of elevation. Scintillation indices decreased with increasing angle of elevation at 1200 and 2980 Mc/s; fitting a curve of the slant range to the irregularities to the data points yielded a best fit in the 1-2 km height region. Ionospheric scintillations at 63 and 112 Mc/s showed a wavelength dependence less than lambda; a comparison of 112 and 225 Mc/s data showed a closer approximation to a first power dependence. The hypothesis advanced for poor correlation of theoretical wavelength dependence and data is that the ray path traverses the auroral region and strong scattering results. Zenith angle variation shows a dependence between z (sec i) to the 1/2 power, the near zone case and (sec i) to the 1/2 power, the far zone regime. Differences in indices for Cygnus rise and Cygnus set on the longer wavelengths are attributed to the difference in the magnetic dip angle of the set and the rise positions; higher indices were observed for Cygnus set in the direction of the magnetic declination of 16 degrees W. (Author)

Descriptors :   (*RADIO ASTRONOMY, ATMOSPHERIC REFRACTION), (*ATMOSPHERIC REFRACTION, EXTRATERRESTRIAL RADIO WAVES), IONOSPHERE, TROPOSPHERE, VERY HIGH FREQUENCY, MICROWAVE FREQUENCY, PARABOLIC ANTENNAS, STARS, ELECTRON DENSITY, ATMOSPHERIC SOUNDING

Distribution Statement : APPROVED FOR PUBLIC RELEASE