Ionospheric VHF scattering near the magnetic equator during the International Geophysical Year

Abstract

General results and statistical studies of equatorial VHF oblique ionospheric scatter signals arc presented for one calendar year of t he International Geophysical Year. The equatorial scatter signals were usually stronger than their counterpart at temperate lati t udes. Scattering was observed comparable to t he D-region scatter propagation familiar elsewhere, but usually t he E-region scatter predominated. Scattering via F-region irregu larities was observed at nighttime over a 2580 km path centered about t he magnetic equator. The intense daytime equatorial E-regioll scattering was established to be largely due to irregularities associated with the equatorial electrojet. Its communications potentialities appear promising for patlls having midpoints within a 10° band of latitude centered about t he magnetic eq uator. When t he D-region scattering was distinguishable, it usually appeared to be stronger than t hat over similar paths at temperate latit udes. However, during the daytime over a path centered just at t he magnetic equator, this comparison is just the opposite. R.elatively st rong scattering from irregularities in the E region was also observed at n ighttime, with the result that the weakest signals received diurnally over the equatorial paths were comparable to the strongest signals propagated over similar paths at temperate latitudes. Both the daytime and nighttime scattering via E-region irregularities exhibited an asymmetry about the magnetic cquator, being stronger for a path midpoint 5° south of tbe magnetic equator tban for a midpoint a similar distance to t bc north.