摘要：

It is well known that the TEC and the foF2 variability differ significantly. However, it has been shown (Xenos et al 2000) that in TEC prediction models foF2 could be used successfully as an index. Therefore, we believe that it is reasonable to investigate the variability correlation between foF2 and TEC. In this paper hourly daily F2-layer critical frequency data recorded at Rome and Juliusruh and TEC data recorded at Flo- rence, Graz and Neusterlitz are used and the relevant variabilities are calculated. It is assessed that there is no clear evidence of their correlation. Therefore, the normalised foF2 and TEC (dfoF2 and dTEC) were then used together with a new index. The new index is the ratio between the differences of ap at the beginning and the end of each ge- omagnetic disturbance and the corresponding differences of the index R. It is pointed out that in winter and when the above new index is negative either dfoF2 or dTEC will be negative but never both, whereas they may both be positive but for less than 10% of the time. In summer, when the above index is negative both dfoF2 and dTEC decrease; whereas when the index is positive, a positive dfoF2 corresponds almost always to a positive dTEC, but a negative dfoF2 may equiprobably correspond to a positive or negative dTEC. Reference Xenos T. D., Spalla P., Mitchell C. N.(2000) Neural Network Based TEC Forecasting Models, Millenium Conf. On Ant and Prop., Davos April 2000.

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