Preliminary results on the within-the-hour ionospheric variability

Studying the variations of the within-the-hour relative deviations of daily 5-minutes measurements of the critical frequencies f_oF2, f_oE and the propagation factor M(3000)F2, it is shown that the deviations of these parameters follow a different statistical distribution in different percentages of the time in each month. Latitudinal dependences of the within-the-hour variability are investigated. Finally comparisons between distributions lead to preliminary quantitative specifications of the within-the-hour variability for each of the examined ionospheric parameters.