Accession Number : AD0717694

Title :   Global Morphology of Ionospheric Scintillations.

Descriptive Note : Environmental research papers,

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

Personal Author(s) : Aarons,Jules ; Whitney,Herbert E. ; Allen,Richard S.

Report Date : 16 OCT 1970

Pagination or Media Count : 40

Abstract : Amplitude fluctuations produced by small irregularities in electron density in the F-layer of the ionosphere (at 300 to 400 km height) can be a problem to communication and navigation systems in the VHF-UHF range. Recent measurements, primarily by AFCRL, are shown with emphasis on results at high and equatorial latitudes. At high latitudes an irregularity region exists whose lower boundary reaches 57 degrees invariant latitude near midnight. During magnetic storms the boundary descends to lower latitudes and the fading becomes deeper. Over the polar cap scintillations are somewhat diminished. When observing synchronous satellites through the irregularity region, deep and fast fading is frequently seen, with fade rates to one per second. Irregularities produce deep scintillations in the VHF range plus or minus 15 degrees from the geomagnetic equator. In equatorial regions maximum occurrence of high level scintillations takes place between 2100 and 2400 local time during the equinoxes; a minimum occurrence is observed during the solstices. When the sunspot number decreases, the equatorial irregularity region spreads and becomes larger. The data for various latitudes has been placed in statistical form, that is, distribution of amplitudes for 15-min samples as well as for periods of 1 yr and longer. (Author)

Descriptors :   (*IONOSPHERIC DISTURBANCES, ELECTRON DENSITY), (*IONOSPHERIC PROPAGATION, RADIO WAVES), VERY HIGH FREQUENCY, ULTRAHIGH FREQUENCY, SCINTILLATION, SUNSPOTS, ATTENUATION, MAGNETIC STORMS, SYNCHRONOUS SATELLITES, POLAR REGIONS

Subject Categories : Atmospheric Physics
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE