Heater-Generated Intermediate-Scale Irregularities; Spatial Distribution and Spectral Characteristics

摘要

The first extensive phase scintillation measurements during both over-and underdense heating are described. The data were collected from an aircraft, and by making repeated scans in the vicinity of the heated volume, the overall spatial distribution of intermediate-scale irregularities has been established. During overdense heating, the irregularities maximize in strength near the HF reflection height, but also map downward at least 100 km with only moderate weakening. From the relative frequency shifts of the phase spectra measured for different directions of aircraft motion, the irregularity anisotropy and drift have also been estimated. The change in phase spectra shape between 6.2 MHz and 9.9 MHz overdose heating is consistent with thermal self-focusing irregularity generation. Underdense heating produces a different phase spectral signature than is theoretically predicted, although enhanced energy does occur at scintillation producing scale sizes. (Author)