Abstract :
There is a pronounced, permanent, variable frequency banded enhancement in high frequency spectra recorded in the ionospheric electron plasma on APEX and CORONAS-I. Spectral characteristics of this banded structure in diverse geophysical regions are discussed. The local plasma density derived with independent techniques is crucial for the interpretation of the banded enhancement. The quasi-simultaneous local plasma density is derived from the antenna impedance measurement, artificial electron beam induced spectra and topside sounder data. Equivalent circuit simulations of wave and impedance measurements reveal spectral signatures of cold plasma density, which match both types of data recorded under stationary conditions. The major spectral characteristics of the banded enhancement are also consistent with equivalent circuit simulations. The data and simulations suggest that the upper hybrid band may be misinterpreted as a circuit resonance. Circuit resonance can be neatly controlled to provide very low interference technique to monitor the density of cold plasma. Circuit resonance monitoring, if properly coupled with impedance measurements and electron beam injection may be a very useful low interference tool for diagnostics of highly structured plasmas like those in the auroral region.
