Accession Number : AD0602546

Title :   RESEARCH ON SPREAD-F STUDIES.

Descriptive Note : Final rept.

Corporate Author : AVCO CORP WILMINGTON MASS RESEARCH AND ADVANCED DEVELOPMENT DIV

Personal Author(s) : Herman,John R.

Report Date : 31 JAN 1964

Pagination or Media Count : 86

Abstract : The results of ionospheric observations using a variety of techniques are summarized to show that magnetic-fieldaligned irregularities exist in the ionosphere. A critique of theories explaining why the irregularities cause spread echoes is given. Statistical studies of the geographic and temporal variations in spread-F occurrence are summarized. The fundamental question of how irregularities causing spread F are produced in the ionosphere is discussed. It is suggested that incoming charged particles traveling down magnetic-field lines to F-region heights create field-aligned ionization which is masked during the day by photoionization. The proposed mechanism is supported by observational results in polar regions. A theoretical treatment of the formation of the ionosphere over the pole at winter solstice indicates that photoionization alone is inadequate to explain observed electron densities in the F layer, and an additional production mechanism such as incoming charged particles is needed. A study of traveling disturbances at high latitudes reveals that the phenomenon is invariably followed by spread-F conditions. An analysis of WWV reception at high latitude is discussed to show the effects of spread F on high-frequency (HF) communications circuits. (Author)

Descriptors :   (*IONOSPHERIC DISTURBANCES, GEOMAGNETISM), RADIOFREQUENCY INTERFERENCE, HIGH FREQUENCY, GAS IONIZATION, PHOTOCHEMICAL REACTIONS, POLAR REGIONS, ELECTRON DENSITY, RADIO ASTRONOMY, ATMOSPHERIC SOUNDING

Distribution Statement : APPROVED FOR PUBLIC RELEASE