Evaluation of the ionospheric noise and variability within the hour by 5 minutes ionospheric soundings

The actual future needs in radio propagation predictions are short-term ionospheric forecasting and now-casting. These are often given at standard hours, but in order to improve the reliability and the accuracy of forecasting, the variability within-the-hour and the so-called “intrinsic noise” of the ionosphere cannot be neglected anymore. Values of f_oF2 and MUF(3000)F2, obtained in 5-minutes vertical sounding campaigns, performed at Rome and Juliusruh ionospheric stations during different seasons and different levels of solar activity, are analysed and the results are discussed.