Electron density profiles in the ionospheric D-region estimated from MF radio wave absorption Original Research Article

Electron density measurements in the lower ionosphere were carried out more than 6 times during the period from 1975 to 1992 by using sounding rockets launched at KSC (Kagoshima Space Center in Japan). Low electron densities were estimated from the absorption of the characteristic mode of ground-based radio signals (17.4 kHz and 873 kHz) in the lower ionosphere measured by onboard receivers. Two kind of methods, i.e., VLF mode absorption and MF absorption methods were developed to estimate the D-region electron density by comparing the observed wave intensity with that calculated by a full wave treatment. In this paper, both absorption methods are introduced paying attention to the capability of low electron density measurement. In particular the S-310-18 rocket experiment is discussed in detail, in which the D-region electron density profile derived from the altitude variation of MF radio wave intensity is presented. Finally the lower ionospheric electron density profiles so far measured by those method at mid-latitude in Japan are compared with those of the IRI-95 model.