D region electron-density distributions from propagation data

By using a fullwave computer program, Deeks was able to find an electron-density distribution in the D region which would account for certain v.l.f. and l.f. propagation results. Here, more extensive experimental results are employed for this purpose; in particular, ground-interference patterns on 16 and 21 kHz. Stationary-phase techniques are developed to enable such patterns to be calculated from an assumed distribution. It is found that, to get the best fit, Deeks´s distribution has to be modified appreciably; the required change can be described roughly as reducing its height by about 6 km.