Preliminary results of scintillation measurements associated with ionosphere Heating and possible implications for the solar power satellite

Initial results of ground and air‐borne measurements of 250 MHz scintillations associated with ionospheric heating in both the overdense (heater frequency below the critical frequency) and underdense cases (heater frequency above the critical frequency) by the high‐power, high‐frequency transmitter at Platteville, Colorado are discussed. The ground stations and the geostationary satellites used in the experiment were so chosen that it was possible to explore the artificial irregularities both within and outside the central heated volume. One ground station was able to view LES‐8 in a field‐aligned direction while, at a second ground station, spaced receiver scintillation measurements were available using FLEETSATCOM. The instrumented aircraft recorded both phase and amplitude scintillations and flew missions in the north‐south and east‐west directions to define the region of artificial irregularities. The preliminary results indicate a prompt excitation of artificial irregularities in the overdense case causing 2‐10 dB scintillation at 244‐249 MHz and a lifetime of the order often minutes. In the underdense case, on the other hand, the response was delayed and effects were observed to be on the order of 1‐3 dB at 250 MHz, although a unique event of 10 dB scintillation was recorded along the field‐aligned propagation path. The presence of such scintillations in the underdense case and their implications for the proposed Solar Power Satellite (SPS) are indicated in the paper.