Analysis of the width of chirpsounder spectra

The chirpsounder technique and the Swedish network of oblique sounders is briefly described. One aim of the present investigation is to provide theoretical support for the evaluation of the recordings from this network. The authors derive an analytic expression for the detected chirpsounder signal assuming single-path propagation through a smooth ionosphere without irregularities. They also obtain a formula that relates the slope of the group time delay curve to the spectral width of the dechirped receiver signal. Analyses of experimental data for smooth ionospheric conditions and simulations of the corresponding situations with a computer program show that the theory agrees well with reality as long as the O- and X-mode traces can be resolved. These analyses are presented together with a discussion of the results of similar experiments reported in the literature