Tatsuo Shimazaki

Effect of the Sq current system on the ionospheric E- and F1-layers

The discrepancy between the observed f0E or f0F1 and those predicted by the Chapman theory was examined in detail. The result shows that the F1-layer varies in a manner more regular than the E-layer, and that the discrepancy in the E-layer may be attributed partly to the effect of scale height gradient, but the principal cause certainly lies in the effect of Sq overhead current system. Discussion is made on the non-uniform motion of vertical drift velocity produced by this effect, as well as on the recombination coefficient and the scale height gradient in these regions.

On the world-wide component of variations in the E-layer ionisation

A method is worked out to obtain the most reliable annual variation in the generalized E-layer character figure, K, in the equation (ƒ0E)4 = K. (cos χ)y, for some particular fluxes of solar radio noise intensity. The method is applied to large amount of data during 10 years, and the world-wide non-seasonal component of variations in this quantity are obtained. For both annual and semi-annual components of variations, the amplitude and phase are determined and discussed. The origins of these components are also discussed.

Dynamical structure of the ionospheric F2-layer as deduced from the world-wide daily variations

Abstract Recourse was made to numerical calculations to find the effects of various non-uniform vertical motions due to diffusion, thermal and/or tidal variations on daily variations in the F 2-layer. A method of solving the problem was worked out so that the electron density distribution may return back every 24 hr regardless of non-recurrent motions of each part resulted by several causes. The comparison of calculated and observed variations shows that the Bradbury model is better than the Chapman model in every respect. Special emphasis is placed upon the fact that the effect of non-uniform semi-diurnal vertical drift velocities with height gradient of both amplitude and phase is very important except near the equator.