Coefficient of electron losses in D region of the ionosphere

The data on the coefficient of the electron losses phi in the low ionosphere were summarized and various models of ionization-recombination cycle in the D region were considered. In high-altitude distributions of phi observed is a sharp transition from low values of phi to high ones at the mesopause level. During ionosphere disturbances the phi value in the region below the given level decreases as compared with normal values at the same heights. The minimum values of phi are obtained during intensive day disturbances of absorption type in the Polar cap. During solar eclipses and at night the value of phi increases significantly as compared to the values, observed under the conditions of full illumination. Considered are the models of ionosphere processes aimed at interpretation of experimental data on coefficient of electron losses and on ion composition variations of the D region. Special attention is paid to hexaion model suggested by Mitra and Rowe. It is shown, that semiempiric models describe qualitatively well the experimental data