Ten‐Point Method of lonogram Reduction

Abstract

The “ten‐point” manual method of ionogram reduction provides true heights at selected frequencies. The method is especially convenient when only the height of maximum density is required, but it can also be used to obtain the complete profile. A single true height is obtained as the average of ten virtual heights sampled at fixed submultiples of the frequency. The sampling points, which depend on the geomagnetic parameters, may be rapidly selected by using the appropriate transparent overlay. A correction for underlying ionization may be incorporated by reading one virtual height from the extraordinary trace.