Modeling of the <Emphasis Type="Italic">D</Emphasis>-region behavior in the polar ionosphere during the solar flare of April 5, 2004

On the basis of the ion chemistry theoretical model, the impact of a powerful solar flare on variations in the ion composition and electron density in the D region of the polar ionosphere is considered. Good agreemnt between the model profiles of the electron density N _e (h) and the experimental data obtained during the flare by the partial reflection method is found. It is shown that the decrease in the effective recombination coefficient observed during disturbances is explained by the depletion of the relative content of the rapidly recombining complex ion clusters.