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The reconciliation of an F ‐region irregularity model with sunspot cycle variations in spread‐ F occurrence
Author(s) -
Singleton D. G.
Publication year - 1977
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/rs012i001p00107
Subject(s) - sunspot , middle latitudes , scintillation , ionosphere , sunspot number , physics , amplitude , electron density , astrophysics , atmospheric sciences , mathematics , electron , climatology , meteorology , solar cycle , geology , geophysics , optics , magnetic field , solar wind , quantum mechanics , detector
A recently proposed means of combining models of ionospheric F ‐layer peak electron density and irregularity incremental electron density (Δ N ) so as to simulate the global occurrence probability of the frequency‐spreading component of spread‐ F is discussed. This procedure is then used to model experimental spread‐ F occurrence results. It is found possible to readily simulate the sunspot‐maximum results, independently of season, with only small adjustments to the amplitudes of the empirical expressions used to model Δ N in the several latitude regimes. However, at sunspot minimum and for each season, the Δ N model requires modification in the equatorial and midlatitude regions of high irregularity incidence, before successful simulations of the spread‐ F data can be obtained. These modifications, which include a broadening of the equatorial region and a poleward shift of the midlatitude region with decreasing sunspot number, are discussed in detail. It is concluded that the scintillation data base, from which the original Δ N model derives, is not sufficiently representative with regard to sunspot number and magnetic index. The use of the spread‐ F adaptation of the Δ N model, as well as its original scintillation version, to rectify these failings of the Δ N model are also discussed.