Proceedings with Extended Abstracts (single PDF file) - Radio ...

Extension of the Kolmogorov spectrumdue to the presence of aerosol particles?Fig. 2 Schematics of Kolmogorov spectrum showing the transition from turbulent or laminarmotions in the inertial-convective subrange into thermal motions at higher spatial wavenumbersk in the viscous-diffusive subrange. Coherent scatter occurs when irregularities ofrefractive index exist at small wavenumbers in the inertial subrange. Incoherent scatter occursin the ionosphere when only thermal motions of neutrals, ions and electrons exist far beyondthe viscous-diffusive subrange. This subrange can be extended into higher spatial wavenumbersof the electron gas when heavy charged particles exist in the ionospheric plasma,which reduce the diffusivity of the electrons. Then coherent scatter can even occur at highspatial wavenumbers, i.e. at higher radar frequencies. The two arrows point to estimates ofradar reflectivity in the D-region for incoherent scatter and coherent scatter (adapted from theWoodman and Guillen paper, 1972), which can merge under such conditions (l.-h. panel).No cooling but PMSEcontamination !(decrease inspectrum width)Fig. 3 Spectra of scatter signals observed as function of height in the mesosphere with theESR on 500 MHz. The enhanced signal around 85 km is caused by coherent scatter fromPMSE irregularities which is superimposed on the incoherent scatter, which dominates belowand above this altitude. The coherent scatter spectrum is narrower than the incoherent scatterspectrum, which could be interpreted to result from a cooler medium if one would disregardthe fact that these are PMSE caused by reduced electron diffusivity.107