Anomalous absorption of a radio wave in the ionosphere

Abstract

A radio wave transmitted into the ionosphere in the presence of a lower-hybrid drift wave excites a Langmuir wave, which is then damped by electrons, thereby heating them. This constitutes an important absorption mechanism. We evaluate the potential of the Langmuir wave and obtain an expression for the ratio Pr of the power of the Langmuir wave to that of the incident radio wave in the inhomogeneous ionosphere. It is found that the radio wave suffers an absorption of about 8% for a density fluctuation n1/n0 = 5%, but the electric field of the Langmuir wave becomes about 11.7 times that of the radio wave, which can lead to the excitation of parametric instabilities in the ionosphere.