Observations of artificially produced scintillations using satellite transmissions

The ionospheric modification experiment, utilizing a high-powered transmitter, provides an opportunity to study ionospheric irregularities under relatively known conditions. The irregularities were studied by means of transionospheric signals from the polar-orbiting satellite ESSA 8 transmitting at 137 MHz. These observations show that scintillations occur when the satellite to ground station geometry is such that the ray from the satellite passes through the region in the ionosphere under modification. In general, a cut across the illuminated volume is obtained; thus an active region of about 100 km in diameter is indicated. For the most part, the artificial scintillations appear to be similar to those obtained from naturally occurring irregularities, but a systematic change from 3 to 1 sec in the fluctuation period is usually observed as the satellite traverses from the northern to the southern portions of the active region. The change in period appears to be produced by a systematic change in irregularity scale size from about 4 to about 1 km.