Studies of Nonlinear Ionospheric Plasma Effect at Arecibo

电离层是高层大气吸收太阳紫外线而产生的传导区。它与无线电波强烈相互作用，并根据频率的不同反射、折射和吸收无线电波。当受到足够强的适当频率的无线电波照射时，它将吸收足够的能量来加热，形成局部的等离子体密度增强，发出高能电子，并发出光。根据这项合同正在探索的方法涉及两个频率间隔很近的无线电波束的辐射，预计这将在拍频产生电离层振荡，从而充当极低频率的无线电发射机，而不需要在表面上安装巨大的天线。这项工作提供了对电离介质的基本物理的见解，并可能在通信方面有实际应用。

The Ionosphere is the conducting region of the upper atmosphere produced by absorbtion of solar ultraviolet light. It interacts strongly with radio waves and reflects, refracts and absorbs them depending on the frequency. When irradiated with sufficiently powerful radio waves of appropriate frequency it will absorb sufficient power to become heated, form localised plasma density enhancements, emit energetic electrons, and emit light. The approach being explored under this award involves irradiation by two radio beams with closely spaced frequencies, which are expected to produce ionospheric oscillations at the beat frequency, and thus act as a radio transmitter for very low frequencies without the need for a huge antenna on the surface. This work provides insights into the fundamental physics of ionized media, and may have practical applications for communication.