ESTIMATION OF PLASMA-DENSITY FROM WAVE DATA OF COLD ELECTRON-PLASMA

Based on the dispersion relation of electron plasma, one can expect, that the waves excited in the frequency band (f(p),f(u)=sqrt(f(p)*f(p)+f(c)*f(c))) should persist in experimental spectra. For wave data from a spacecraft immersed in a cold plasma such an assumption may be misleading. In measurements performed on the board the INTERCOSMOS-19, ACTIVE, APEX satellites and VC36.064CE rocket the most prominent spectral structure is centered around frequency fr fulfilling the relation f(c)<f(p)<f(p) and corresponds to resonant detection of Bernstein waves excited in the surrounding plasma by spacecraft systems. Input network mismatch at frequencies around fu significantly depresses natural plasma noise as well as that excited by the spacecraft. Plasma emissions in the band (f(p),f(u)) are prominent if the electromagnetic excitation is preferential (topside sounders) or if the excitation introduces nonequilibrium components into the plasma e.g. particle beams or clouds. Experimental examples are presented and parameters of cold plasma spectra useful for electron density estimation are discussed. The application to other spacecraft-cold plasma configurations is suggested.