Statistical characterization of the ionosphere using GPS signals

In this paper, the variability of the ionosphere is examined using Vertical TEC (VTEC) estimates obtained from CPS signals. The statistical structure of the ionosphere is investigated by making use of a sliding window mean and a variance of the estimated VTEC data. The choice of the sliding window size is based on the estimated variance of the first and second order moments. The investigation technique is applied to a data set obtained from the solar maximum period during April 23-28, 2001, for typical high and mid latitude stations. During the quiet day of this period, it is slowly time varying and locally stationary in a sliding window of 15 to 20 minutes. The wide sense stationarity period of the high latitude station, both for quiet and disturbed days, is shorter than those for the mid-latitude stations, which indicates the higher variability of ionosphere for high latitudes.