Model studies of the kinked Z trace in topside ionograms

The propagation characteristics of the Z trace observed on topside ionograms are reviewed. One feature, the "kinked" Z trace, is examined in detail. It is shown that the kink can be explained by simple magnetoionic theory and is not due to peculiar electron density distributions. A ray tracing propagation analysis confirms this contention. Although the Z trace normally does not propagate down to the Flayer peak, its inherent resolution is superior to that of the ordinary and extraordinary modes. Its use in ionogram analysis may thus improve the accuracy of electron density profile calculations.