Triple splitting and z-rays in polar ionograms

Abstract

The theory of propagation in a direction almost parallel to the Earth’s magnetic field is reviewed, calculating the group refractive index of the ordinary ray in the presence of electron-neutral collisions. An electron density profile is estimated from the ordinary trace and is used to compute the z-ray trace. It is shown that this reconstruction can help to identify the rare cases of z-rays from among the numerous cases of duplicate ordinary traces, due to reflection from two different directions. Received 13 June 2014, accepted 10 December 2014