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 ion ospheric forecasting and nowcasting. These are often given at standard hour s, 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(o)F2 and MUF(3000)F2, obtained in 5-minutes vertical sounding campaigns, performed at Rome and Ju liusruh ionospheric stations during different seasons and different levels of solar activity, are analysed and the results are discussed. (C) 2001 Els evier Science Ltd. Ail rights reserved.