Physics of Thermal Cavitons

本课题对热空腔的物理特性进行了实验和理论研究。电离层可以被认为是一个巨大的、没有边界的天然等离子体实验室，具有很好的等离子体约束。在用长时间、高功率高频（HF）无线电波加热的电离层改造实验中，观察到大规模（超过几十公里）密度消耗（近50%密度改造）。这一现象的基本过程可以用高频反射层附近等离子体的欧姆加热和随后等离子体从该层排出来理解。因此，“这些密度消耗被称为‘热空腔’。最近在波多黎各阿雷西博进行的电离层修饰实验结果表明：1)高频反射层附近的电子温度升高“大约是初始温度的5倍”；2)雷达观测表明热空腔内存在强离子湍流；3)热空腔可以与自然产生的密度气泡相互作用。热空腔的大小有时对于注入电离层的电磁能量来说显得太大了。为了解决这一问题，本文提出了一种新的输运模型，该模型通过现象效应使注入的电磁波由于背景等离子体中的初始弱密度空腔而自聚焦。模型方程的数值分析似乎表明，我们是在正确的轨道上。一些实验室实验研究了短时间尺度等离子体湍流对热腔的影响。

Physics of thermal cavitons has been investigated experimentally and theoretically in this research project.The ionosphere can be considered a natural plasma laboratory of great size with no boundaries and an execllent plasma confinement. During ionospheric modification experiments with "long-time, high-power high-frequency (HF) radio wave heating, large-scale (over a few tens of" kilometers) density depletions (nearly 50% density modification) have been observed. Basic processes of this phenomenon can be understood in terms of the Ohmic heating of the plasma "near the HF reflection layer and the subsequent plasma expulsion from this layer. As a result, " these density depletions are dubbed 'thermal cavitons'.The results of recent ionospheric modification experiments performed at Arecibo, Puerto Rico, have revealed that 1)the increase in the electron temperature near the HF reflection layer is "roughly 5 times the initial one, 2) radar observations suggest the existence of strong ion" "turbulence inside thermal cavitons, and 3) thermal cavitons can interact with naturally" generated density bubbles.The size of a thermal caviton sometimes appears too large for the electromagnetic energy "injected into the ionosphere. In order to solve this problem, a new transport model has been" "introduced, in which the self-focusing of the injected em wave due to an initial weak density" cavity in a background plasma is phonomenologically imposed. Numerical analysis of the model equations appear to indicate that we are on the right track.Some laboratory experiments have been performed to investigate the effects of short-time scale plasma turbulence on thermal cavitons.