Fig. 2.From: A comparison of the equatorial spread F derived by the International Reference Ionosphere and the S4 index observed by FORMOSAT-3/COSMIC during the solar minimum period of 2007–2009Variations of the F10.7 and the Spread-F occurrence probability in the Brazilian region during 2000–2009. (a) F10.7 solar radio flux (b) Spread-F occurrence probability derived from IRI-2007. F10.7 shows that it is solar minimum during 2007–2009 (denoted by the red curve).Back to article page