Geomagnetic Control of F 2 Layer Ionization

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Abstract
The equinox phenomena experienced at stations situated between magnetic latitudes [plus or minus]18[degree] are similar to those experienced at Slough, England (lat. 51[degree]30[image]N) in a northern summer, when the ionization in the F layer as a whole is distributed through a great range of vertical heights. At Slough in winter, the F layer is fairly homogeneous and the ionization density is high, whereas in summer, under conditions of reduced solar zenith distance, there is marked bifurcation of the layer into its 2 components and the ionization of the upper component (F2 layer) is much reduced and this layer exhibits entirely different characteristics. The electron production rate at the layer maximum is much reduced, as is also the electron recombination coeff. The variation of ionization is no longer substantially symmetrical about noon. At [plus or minus]18[degree] magnetic latitude the ionization maxima are associated with a relatively thin homogeneous F layer without marked bifurcation. The long study of F2 layer ionization has shown that, as in the case of the E and F1 layers, there is marked variation of ionization in sympathy with the trend of the sunspot cycle. In addition, the ratio [image] max./[image] min., where these terms refer to noon ionization densities at sunspot maximum and minimum, respectively, is not constant at any station for each month in the year. A study of similar phenomena at stations other than Slough suggests that it is the seasonal variation of the atmospheric medium which is substantially responsible.
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