Estimation of electron density of ionospheric plasma using wave, impedance and topside sounder data

Abstract

Instability analysis of the dispersion relation of electron plasma indicates that enhanced emission in the frequency band ( fp,fu=sqrt(fp ∗fp+fc ∗fc ) can be easily detected in wave spectra of space plasmas. Such emission, in passive mode spectra, can be used to determine plasma density of the major cold plasma component and points out the existence of a minor energetic component. Contrary to such expectations, it was shown that in passive measurements performed on the INTERCOSMOS19, ACTIVE and APEX low-altitude satellites, the most prominent and persistent spectral structure was centered around frequency fr fulfilling the relation fc<fr<fp and corresponded to resonant properties of the equivalent input network. The input network mismatch at frequencies around fp significantly depressed natural plasma noise and made it hardly discernible. Plasma emissions in the band (fp,fu) were prominent when propagation properties of electromagnetic excitation were dominating (topside sounder) or if the excitation introduced a sufficient amount of nonequilibrium components into the plasma in the form of an injected electron beam. The wave, impedance and topside sounder data, registered on the recently launched CORONAS low-altitude satellite, support and supplement previous observations and interpretation. Analysis of pertinent CORONAS data in various geophysical regions is presented in this paper. Consistency of wave and impedance experimental spectra with their equivalent circuit simulations and topside sounder data is obtained. Data and simulations argue against permanent observability of the upper hybrid band in ionospheric plasma.