Ionospheric irregularities produced by internal atmospheric gravity waves

Abstract

A perturbation treatment is used to determine the nature and magnitude of the effects of internal atmospheric gravity waves on the ambient rates of production, chemical loss, and motion of the ionization. The relative and absolute importance of these effects in the creation of ionospheric irregularities are assessed. This assessment yields several conclusions of particular interest. Firstly, in the F2-region the dominant effect of the gravity waves is that of imparting the motion of the neutral gas parallel to the magnetic field to the ionization through collisional interaction. Secondly, at heights at or below the height of the F1-ledge, chemical effects, in particular the effect of gravity waves on the rate of photoionization, are quite important. Thirdly, gravity waves affect the rate of photoionization at a given point by changing both the neutral gas number density and the ionizing radiation flux at that point, and this latter effect, hitherto ignored, is in some respects the more important of the two. Fourthly, as a result of the interplay of a number of factors, certain Fourier components of that portion of the gravity-wave spectrum permitted at ionospheric heights are more successful than others in creating observable disturbances. Finally, gravity waves creating neutral gas velocities of the order of 20 m sec −1 seem capable under the right conditions of creating TID's of the largest magnitudes observed.