observations resulted from modification using radio waves that resonated with the ionospheric plasma. The SPS frequency is orders of magnitude above the ionospheric plasma frequency so the mechanism that apparently produced all of the field-aligned scatter in the past will not be triggered by the SPS. The question arises, will the microwave beam produce any effects that would generate field-aligned scatter. In one scenario the kilometer scale striations produced by thermal self-focusing (Sec. 2.2.1) might cascade energy into meter-length striations (field-aligned scatterers). Although no conclusive tests have been performed, tests using available modifiers at the Arecibo Observatory gave no observable field-aligned scatter (scattering cross section below 10-3 m2) for a 50 MHz radar on Guadeloupe at a site selected to satisfy the aspect sensitivity of the scatter. The available modifiers failed to simulate the SPS effects in incident power density and/or volume affected.
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