Relative amplitude of the variations of the total electron content according to the data of the GPS global network

[1] A method is developed that makes it possible to estimate the relative amplitude dI/I of the variations of the total electron content (TEC) corresponding to the mean (MS) and intermediate (IS) scales of ionospheric irregularities (from 300 to 30 km). This method is based on the evaluation of TEC variations from the data of the global GPS network. The results of the analysis of the diurnal and latitudinal dependencies of dI/I and distribution probability P(dI/I) for 52 days with different level of geomagnetic activity are presented. The statistical estimates were obtained from the analysis of 10 super(6) samples of 2-hour-long TEC series. To obtain statistically significant results, we have chosen three latitudinal zones provided on the Web by the maximum number of GPS sites: high-latitudinal zone of the Northern America (50-80 super(o) N, 200-300 super(o) E; 59 stations), midlatitude zone of the Northern America (20-50 super(o) N, 200-300 super(o) E; 817 stations), and the equatorial zone (20 super(o) S-20 super(o) N, 0-360 super(o) E; 76 stations). It was found that on the average the relative amplitude of the TEC variations varies within the range 0-10% proportionally to the value of the Kp geomagnetic index. This dependence is best pronounced at high latitudes (the proportionality coefficient k = 0.37), is weaker at middle latitudes (k = 0.2), and is the weakest at the equator (k