标题：A comparison of the equatorial spread F derived by the International Reference Ionosphere and the S 4 index observed by FORMOSAT-3/COSMIC during the solar minimum period of 2007–2009
摘要：The latest version of the International Reference Ionosphere (IRI-2007) model includes an option for spread- F occurrence prediction for the first-time.The IRI-2007 spread- F occurrence is a function of solar 10.7 cm radiation flux, F 10.7.In this paper, an attempt is made to cross-examine the spread- F occurrence derived by the IRI-2007 and the ionospheric scintillations in terms of the maximum value of the S 4 index ( S 4max) between 150–350-km altitudes, calculated from fluctuations of the signal-to-noise ratio (SNR) intensity in the L1 channel of GPS radio occultation signals using FORMOSAT-3/COSMIC (F3/C) satellites during the low solar activity years 2007–2009.It is found that S 4max maintains a fairly good consistency with spread- F occurrence simulated by IRI-2007 in the Brazilian region.Thus, the global S 4 index statistics can be considered as a viable source of database to be incorporated into the global IRI spread- F prediction scheme owing to fact that the F3/C satellites can provide an unprecedented global database including the S 4 index.
关键词：GPS RO technique ; S 4 index ;IRI-2007 ;spread-F
