A method for assessing the characteristics of small-scale ionospheric inhomogeneities based on GPS monitoring results

Abstract

A method has been developed for processing measurement results of the total electronic content of the ionosphere using signals from global navigation satellite systems GPS/GLONASS. It allows to es timate the root mean square of small scale fluctuations of the total electronic content and the aver age (characteristic) size of small scale ionospheric inhomogeneities. The proposed method is based on a modification of the GPStation 6 dual frequency receiver, which allows to significantly increase the sampling rate of measurements of the total electronic content and reduce the level of instrumental noise, and on the use of a discrete digital Butterworth filter to isolate small scale fluctuations of the to tal electronic content. As a result of the analysis of the process of measuring the total electronic content of inhomogeneous ionosphere using GPS/GLONASS signals and a modified dual frequency receiver GPStation 6, the cutoff frequencies of the bandpass filter used are justified: 1 and 10 Hz. Considering that such a filter should simultaneously have the smoothest possible amplitude frequency response at transmission frequencies and should not introduce a large group delay into the measurement results, the use of a Butterworth filter of the 6th order is justified. It is shown that the analysis of the autocor relation function of small scale fluctuations of total electron content makes it possible to estimate the average size of the small scale ionospheric inhomogeneities causing such fluctuations at the heights of maximum ionospheric ionization.