| A renomalization technique, employed in the spirit of the formal theory of scattering, is applied to the problem of ionospheric scintillation. Using the forward scattering approximation for wave propagation and a Markov approximation for ionospheric fluctuations, one derives renomalized moment equations descriptive of the wave statistics.; The propagation of the two and four point wave statistics thru^the ionosphere are obtained using a slow quasiparticle distribution^function S. For the case of an ionospheric structure function H( )^= a ('2), where is a transverse distance, one can obtain exact^analytical solutions for the wave statistics. For an arbitrary fluctuation spectrum, one can evaluate the S function along a quasiparticle trajectory and thereby infer second moments exactly and fourth moments approximately. Knowledge of the S function enables one to ascertain statistical properties, such as average intensity, two point intensity correlation and the scintillation index S(,4).; The scintillation index for the case of a plane wave propagating thru the ionosphere is studied for the case of an arbitrary power spectrum of ionospheric fluctuations. Peaks superposed on a power law spectrum are found to increase the value of S(,4). A focusing effect on the S(,4) vs. z variation is observed in the strong scintillation limit.; An experimental power spectrum, corresponding to relative density fluctuations of about 20% as obtained from in situ measurements by the Atmospheric Explorer-E satellite, is used to calculate the corresponding S(,4) for night time equatorial scintillations. For an ionospheric slab model with a thickness of 200 Km and an altitude of 300 Km numerical calculations yield, in approximate agreement with Dr. Basu, an almost saturated scintillation index S(,4) of about 1.1. |
