27tägige Variationen in der D-Schicht-Absorption der Ionosphäre über Singapore und Slough

Abstract

The absorption in the D-layer of the ionosphere is already known to change with the seasons and with the 11-year sunspot cycle. The question has therefore been examined, whether analogous variations occur in the course of the solar rotation of about 27 days in cases where the sunspots are unequally distributed in heliographic longitude (in such cases the sun exhibits, in the course of a rotation, alternatively aspects with many spots and with few spots). Such variations in absorption of appreciable amplitude are found at Singapore during the whole year, at Slough (near London), however, only during the summer months. Other variations in absorption of larger amplitude than in summer are found in Slough during the winter months, but these winter-time variations are not controlled by 27-days variation in sunspot number R and also not by variations in particle radiation. The significance of these results in connection with radiocommunication circuits and for ionospheric forecasting is briefly discussed.