Ionospheric disturbances and gravity waves

In Part I, TIDs are studied by utilizing the set of hydrodynamic equations for electrons, ions and neutrals as well as Maxwell's equations. Equations are grouped into two sets, one describing the motion of charged particles, the other describing that of neutrals. Study here is concerned with the solution of the set of equations for charged particles for the density perturbations of electrons and ions, with coupling terms between neutrals and charged particles on the right hand sides of equations. The solution thus obtained is compared with that based on a diffusion theory. Despite the analytical similarity between the results of two theories, theory presented here, being a dynamical and self-consistent one, provides some important modifications in the treatment of coupling problem between neutrals and charged particles. In Part II, an analytical attempt is made to interpret the multiple traces on an ionogram obtained by a ground sounding for irregularity information. A mathematical expression for the physical process, which returning echoes must satisfy, is sought. This expression is properly manipulated to determine the initial angle of propagation for a returning echo as a function of the horizontal perturbation parameter, α, and x/sub m/, position of center of the maximum perturbation. It is then possible to construct an ionogram theoretically with the aid of ray equation, with α and x/sub m/ as the running variables. Comparison of this theoretically constructed ionogram with the one obtained by observation permits one to determine not only the magnitude of perturbation, α, but also irregularity velocity