On the possible use of recent EUV data for ionospheric predictions

The various ionospheric layers produced and maintained by solar ionizing radiations support a variety of long distance HF communications around the world. Traditionally, long-term ionospheric predictions are based on a predicted qualitative sunspot index and correlations established between observed sunspot indices and ionospheric parameters. As the techniques are esentially statistical, the long series of sunspot observations stand in good stead and have given satisfactory long-term predictions of the monthly median ionospheric parameters. However, with the recent availability of EUV data from satellites, it is considered more appropriate to use these radiations, which are directly responsible for the production of the ionosphere, for prediction purposes rather than the surrogate sunspot index. The present study has shown that the use of EUV flux for ionospheric predictions has certian advantages over the usual solar indices such as R(12) and F(10.7). Saturation effects, that are usually seen in the foF2 variation with sunspot numbers at low latitudes, are not apparent with EUV flux. EUV flux values also require much less smoothing when compared to sunspot numbers and are more suitable for the prediction of ionospheric parameters one or two months in advance.