Scattering of radio waves from great virtual distances

Summary—Using a pulse‐transmitter of high power, scattered reflections corresponding to virtual reflection‐distances of 500 to 2,500 km have been obtained. The test‐frequencies used (10–11 Mc/sec) were usually greater than the critical penetration‐frequencies of the F2‐layer. Records on a fixed frequency over a number of days have been taken in order to study the diurnal variation and dependence on geomagnetic activity and aurora. Four different phases in the diurnal variation have been recorded. During the two day‐phases it has been shown that the scattered reflections cannot come in vertically as they are not cut off by the F‐layer. During the two night‐phases the echoes are reflected from scattering areas lying in or near the zenith at heights of 500 to 800 km. Small geomagnetic disturbances increased the scattering at these heights. Stronger perturbations were accompanied by scattering from heights down to 100 to 200 km.