Response of the ionosphere to the passage of neutral atmospheric waves

Abstract

A series of theoretical calculations of the response of the ionosphere to the passage of neutral atmospheric waves is presented. The results of these calculations should be applicable as a tool for interpreting and assessing the significance of ionospheric drift data. In the F-region of the ionosphere, the ion gyrofrequency is much greater than the ion-neutral collision frequency so the bulk motion of ions is constrained to be along the Earth's magnetic field lines. When the relevant atmospheric wave frequency is much less than the ion-neutral collision frequency, the motion of ions will be in phase with the atmospheric wave but the ionization will take on only the component of the neutral gas motion that is parallel to the Earth's magnetic field. Coulomb forces require corresponding changes in the electron density and the resulting redistribution of the ionization is strongly influenced by the magnetic field orientation relative to the neutral particle trajectories. Based on this model of the interaction between a neutral wave and F-region of the ionosphere, calculations are made of the ionospheric response to several idealized neutral atmospheric wave types. The treatment ignores source and sink mechanisms and seeks solutions of the continuity equation to give the redistribution of ionization under the influence of neutral atmospheric waves as a driving mechanism. Analytic expressions are obtained for the change in the peak electron density and the change in the height of the peak during the passage of a wave. Computer calculations based on the same model permit somewhat less idealized wave and ionospheric characteristics to be used.