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Relation Between the Equatorial Anomaly and Trans‐Equatorial VHF Radio Propagation
Author(s) -
GibsonWilde B. C.
Publication year - 1969
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/rs004i009p00797
Subject(s) - ionosphere , anomaly (physics) , geology , sporadic e propagation , equator , radio propagation , geophysics , magnetic dip , radio wave , ionosonde , latitude , geodesy , physics , electron density , astronomy , plasma , quantum mechanics , condensed matter physics
Comparison of the occurrence of VHF radio propagation over a 6620‐km transequatorial circuit between Korea and northern Australia with the development of the equatorial anomaly in the F layer shows that the transequatorial propagation mechanism is closely related to changes in the form of the equatorial anomaly. Signal occurrences are most common when the anomaly in f o F 2 exhibits sharp well‐defined crests located fairly symmetrically on either side of the dip equator at dip angles between 20° and 30°. These crests correspond to large horizontal gradients in the F layer ionization density, which are known to be capable of refracting radio waves at frequencies well above the normal for a horizontally homogeneous F layer. It is suggested that all transequatorial VHF signal occurrences observed over this circuit can be explained in terms of an F 2 F 2 propagation mode, with the ionospheric refractions occurring at the crests of the equatorial anomaly.