SPECTRAL CHARACTERISTICS OF IONOSPHERIC F-LAYER IRREGULARITIES GENERATED BY ATMOSPHERIC-TURBULENCE

We have calculated spectra of small-scale electric fields generated by atmospheric turbulence in the E-region and transmitted into the F-region of the ionosphere. In the case of a power law spectrum of atmospheric turbulence the calculated spectra of electric field also exhibit a power law part in the region of long wavelengths (over several kilometers). In the short wavelength region the spectrum decreases faster as compared with the power law. It is shown that these electric fields produce electron density irregularities with 1-10% amplitude in the F-region. The calculated spectra of the irregularities exhibit a strong elongation of the irregular structure along the geomagnetic field. A typical longitudinal size of the irregularities is of the order of 100 km, and the transverse size is at least several kilometers. The amplitude of electron density fluctuations obtained from estimations agrees with the observed ; however, the calculated spectra do not show short wavelength irregularities with the size of less than or of the order of 1 km, which disagrees with experimental data. The most likely reason for this discrepancy is that the assumption about the wave-like character of turbulence in the upper atmosphere is untenable (we have used this assumption when calculating plasma density fluctuations). © 1990.