The spectral effect of the density irregularities on the scintillation index of transionospheric signals

Summary form only given. The ionospheric plasma can cause dispersion and spectral broadening of the transionospheric electromagnetic signals due to the presence of the density fluctuation whose effect on the signals received on ground is usually measured in terms of the scintillation index S/sub 4/. Many theories have been proposed in the past to determine S/sub 4/ based on the correlation properties of the wave. In the present work, an alternative approach is used to investigate the ionospheric scintillation problem. The authors model the irregularities in the ionosphere by set of sinusoidal fluctuations, with each fluctuation in the set having a finite uniform spectral distribution and a random phase. Thus the scattering process in the ionosphere is deterministic for each individual scattering event from a single group of finite spectral width sinusoidal density variation. A quasi-particle theory is introduced to analyze the scattering event. It treats the wave as a distribution of quasi-particles in the space described by a Wigner distribution function (WDF). Multiple scattering effects is an intrinsic feature of the transport equation of the WDF. It is manifested by the variations of the quasi-particles distribution caused by collisions of the quasi-particles with the density irregularities. In free space, diffraction effect on the perturbed signal as it propagates from the exit plane of the plasma layer to ground is included by using Fresnel theory. The random nature of the problem accounts for the received signal power spectrum calculated. This semi-deterministic approach can be applied for irregularities having spectral distributions relevant to the experimental observance.