IGY observations of F-layer scatter in the far east

Abstract

Peculiar signal enhancements observed during transmissions at 36 to 50 Mc/s between the Philippines and Okinawa appear to represent F‐layer scatter. These signals are observed nightly for periods of several hours during the months of September and October. Pulse tests indicate F‐layer heights for these signals. Considerable pulse broadening is observed and the signals generally arrive from somewhat off the great circle path.

The postsunset rise offoF2in the transition region and its dependence on the postsunset rise ofh′Fin the equatorial region

“…From a study of true height profiles along 75øW meridian Wright [1960a] has found enhanced ionization density in the transition region in the late evening hours almost simultaneously with the rise in the equatorial F region. High electron densities were also reported at the transitionregion stations like Okinawa and Bo.got• during the late evening hours [Bateman et al, 1959;Gates, 1959]. In the present analysis it is shown that a characteristic postsunset rise of ]oF• occurs in the transition region in all the three (Asian, African, and American) longitudinal zones, and that it is msfinly controlled by solar activity and closely dependent on the height of the F layer in the equatorial region.…”

Preliminary results of the National Bureau of Standards radio and ionospheric observations during the International Geophysical Year

“…A more detailed report of this Far Eastem VHF anomaly has been published [9]. These authors conclude that these anomalous signals arc associated with low-latitude spread F as often recorded by ionosphere sounders and may indicate the presence of field-alined blobs of ionization in the F region.…”

On the nature of equatorial spreadF

“…Comparison with F scatter in the Far East. Other VHF ionospheric forward-scatter studies [Bateman, Finney, Smith, Tveten, and Watts, 1959;Smith and Finney, 1960] have been conducted by the National Bureau of Standards in the Far East, and signals attributed to F scatter have been obtained. The paths over which these signals were propagated were about half as long as the 2580-km circuit discussed in this paper, implying a considerably larger scattering angle.…”