The ionogram


An ionogram is a graph of time-of-flight against transmitted frequency. Each ionospheric layer shows up as an approximately smooth curve, separated from each other by an asymptote at the critical frequency of that layer. The upwardly curving sections at the beginning of each layer are due to the transmitted wave being slowed by, but not reflected from, underlying ionisation which has a plasma frequency close to, but not equaling the transmitted frequency. The critical frequency of each layer is scaled from the asymptote, and the virtual height of each layer is scaled from the lowest point on each curve.

An ionogram can be much more complicated than just two layers. There can also be such phenomenon as;

Ionosondes | WDC

26-JUL-1996 Chris Davis