Use of a Global Effective Sunspot Number IG₁₂ for Long-term Ionospheric Predictions

The possibility of the use of a global effective sunspot number IG₁₂ for long-term ionospheric predictions is investigated in this paper based on the data of vertical incidence sounding stations in China. It is shown that the relationship between the ionos-pherically-derived index IG₁₂ and the ionospheric characteristic (f₀F₂ or F₂(3000)MUF) is better than that between sunspot number R₁₂ and the ionospheric characteristic.The efficacy of the use of IG₁₂ for predicting f₀F₂, M(3000)F₂ and F, (4000)MUFis evaluated, using CCIR Report 340, by comparison with R₁₂ in current use. The evidence presented shows that the use of IG₁₂ instead of R₁₂ in the CCIRprediction scheme yields more accurate values of f₀F₂ and F₂(4000)MUF. In the predictions of f₀F₂ and -F₂(4000)MUF 12-month in advance. The average improvments in accuracy are about 18% and 10% respectively. Other advantages arising from the use of the IG₁₂ index are also discussed.