Intense Es Ionization near the Magnetic Equator

Intense Es Ionization near the Magnetic Equator Worldwide Es ionization was examined from monthly median values of fEs at many stations (see Fig. 1).Meridional distributions of Es ionization on geomagnetic and magnetic latitudes are better arranged than that on geographic latitudes, as well as cases of occurrence-frequencies of Es (1) (2).As shown in Fig. 2, it seems fEs on geomagnetic latitudes in the day-time (mean values from 09h. to 15h.) distributes proportionally to cosx, where x is the sun's zenith distance.(Curves in the figure are obtained assuming that hour-angles are 0 and the sun's north declinations are respectively 3 and 20 for September and May.)But, the ionization near the magnetic equator, for example at Huancayo and Christmas Island, is abnormally large, though such a phenomenon does not occur in