Limitations of Quasi-longitudinal Approximation to the Generalized Magnetoionic Formula in Partial Reflection Experiment

Abstract

The reflection coefficierts <i>R_∞ </i> and <i>R_o </i> and the absorption coefficients <i>F_∞</i> and <i>F_o </i>corresponding to extraordinary and ordinary modes of propagation of radio waves in the ionosphere are evaluated using the generalized magneto ionic formula. These are compared with the results of quasi-longitudinal approximation which is often used for the derivation of electron density from partial reflection measurement The longitudinal approximation fails to notice the inversion in the ratio <i>R_∞/R_o </i> and a change in the sign of <i>(F_∞- F_o </i> in the low altitude region where the electron neutral collision frequency exceeds the operating frequency of the wave and gives erroneous results. At higher altitudes the error in the derivation of the number density of electrons is of the order of 12% at 75° dip, 17% at 45° dip and as high as 300% at 15° dip if the longitudinal approximation is used.