Thin Ionization Layer of the Enhanced Aurora

在近一半的时间里，极光显示出薄而明亮的层，称为“增强极光”。“这些显示器与E区薄、致密、重离子层有关。当波粒相互作用将周围的电子加热到双原子氮的17 eV电离能或略高于17 eV电离能时，就会产生这种现象。有几种可能的等离子体不稳定性可以在薄层中产生超热电子，但没有详细的理论研究如何在薄电离层中发展不稳定性。这个项目将研究在薄的、密集的、重离子层中发生的不稳定性。它将使用广泛的分析与粒子模拟相结合。对交叉场电流不稳定性的初步分析表明，在重离子层中，交叉场电流不稳定性是强不稳定的。初始的静电模拟表明，大量的周围电子的加热发生在氮气电离能或以上的电子。模型的进一步改进将导致与观测的精确比较，使用各种数据，包括地基光学，雷达测量和现场火箭测量。该模型还将用于研究其他竞争性不稳定性，以便建立增强极光的机制。在这个建议中所描述的理论工作和模拟代码也可能有应用程序的不稳定性与杂质在聚变装置中的重离子物种起源于壁和限制器材料已知污染的核心氢等离子体。

Nearly half of the time, auroral displays exhibit thin, bright layers known as "enhanced aurora." These displays are associated with thin, dense, heavy ion layers in the E-region. They result when wave-particle interactions heat ambient electrons to energies at or just above the 17 eV ionization energy of diatomic nitrogen. There are several possible plasma instabilities that could produce suprathermal electrons in thin layers, but there has been no detailed theoretical investigation of how instabilities in the thin ionization layers develop. This project will examine instabilities which would occur in thin, dense, heavy ion layers. It will use extensive analytical analysis combined with particle simulations. A preliminary analysis of a cross field current instability has been found to be strongly unstable in the heavy ion layers. Initial electrostatic simulations show that substantial heating of the ambient electrons occurs with energization at or above the nitrogen ionization energy. Further improvements in the model will lead to precise comparisons with observations, using a variety of data including ground based optics, radar measurements, and in situ rocket measurements. The model will also be used to examine other competing instabilities, so that the mechanism for the enhanced aurora can be established. The theoretical work and simulation code described in this proposal is also likely to have applications to instabilities associated with impurities in fusion devices where heavy ion species originating from the wall and limiter materials are known to contaminate the core hydrogen plasma.