Short-Period Changes in the F Region of the Ionosphere

Abstract

RADIO observations designed to detect horizontal movements in the ionospheric regions and to investigate the relation of these to previously observed changes occurring above a single observing point have been in progress for some months in the vicinity of Sydney, New South Wales. The present system uses three transmitters (T₁, T₂, T₃) placed at the apexes of a right-angled triangle with its shorter sides approximately north-south and east–west and of length 13 miles and 27 miles respectively (Fig. 1). The transmitters are operated on the same frequency and with the same repetition frequency, and are so phased, by either mains synchronization or pulse triggering technique, that the three pulses are spaced about 50 km. apart on a normal type of time base such as is used for ionospheric observations, It is thus possible to record the three sets of echoes simultaneously on a single film. Standard 35-mm. film is used, moved continuously with a film speed of ¾ inch per minute. Observations can be taken at one or more of three points, two being at the most widely spaced transmitting sites (R₁ and R3), and a third at a point approximately midway between these (R₄).