ESTIMATION OF ELECTRON DENSITY AND THE LOWER IONOSPHERE HEIGHT USING THE MULTIMODE TWEEK-ATMOSPHERICS ANALYSIS DATA

Abstract

Tweek-atmospherics (tweeks) together with the transmission of ELF-radio station signals were used for lower ionosphere examination. Both a decrease of and a growth in the effective reflection height with an increasing wave mode order were predicted within the scope of existing models of tweek propagation close to the cutoff frequency of the Earth-ionosphere waveguide. It is for this particular reason that analyzing the experimental data with the updated procedure for making precise estimates of the ionospheric reflection height has awakened a certain interest. The author of the present paper has utilized experimental records of tweek-atmospherics to gauge the distances to their sources as well as the effective ionospheric-reflection heights that are consistent with the 1-st and higher-order modes of the Earth-ionosphere waveguide. A study has also been made into the number of observed harmonics tweeks-containing as a function of the source range, the local time and the effective ionospheric-reflection height. The effective height of tweeks reflection was shown to be rising by night-time. The author has observed the relative number of higher-order harmonic tweeks to grow over the reflection height interval between 87 and 89 km. The peak number of harmonics was observed at the 20 to 24-hour period of local time. It has been demonstrated that the effective reflection height for the 1-st mode exceeds that for the 2-nd mode by more than 1.4 km. It was due to this event that it was feasible to estimate the electron density in the reflection height region within the scope of the anisotropic ionosphere model'. The findings of the study the author was concerned with allowed opting an adequate tweeks propagation model and estimate the lower ionosphere parameters.