Development of an Integrated View of Plasma Instability Processes in the Lower Ionosphere

地球的电离层是中性气体和带电粒子的混合物。电离层通常按层划分，根据最常被吸收的辐射的波长来定义。E区绵延90-150公里，通过X射线和紫外线电离。F区(150-600公里)被极端紫外线辐射电离。虽然波和扰动(“结构”)出现在整个电离层介质(“等离子体”)中，但研究往往侧重于E层或F层，这部分是由于实验和理论上的限制；所采用的技术。因此，对电离层等离子体结构过程的统一看法的发展仍未完成。这一建议将通过以下方式填补这一空白：(1)发展适用于大范围海拔范围的统一的等离子体不稳定理论，包括以前未曾探索过的E和F区峰之间的过渡谷区；(2)用常规接收大范围海拔回波的雷达观测谷区。这项拟议的研究利用了NSF的资产和知识合成，从根本上为等离子体不稳定和结构理论做出了贡献。这些知识与通信和导航行业相关，因此也与社会相关。整合的理论将被纳入UAF等离子体物理课程，目前主要依赖于原始期刊出版物，而不是教学模块。该提案还将资助一名新的博士生。拟议的研究将解决基本问题，即不稳定和稳定因素的组合会导致等离子体扰动的幅度增加并产生电离层结构。实际拟议的活动由三个相互关联的项目组成：1.发展电离层等离子体不稳定性的统一理论，包括对任意高度和传播的热效应、惯性效应和梯度效应；2.确定在任意高度的非等温情况下使等离子体不稳定所需的临界梯度长度；3.分析SuperDARN和ISR数据，以调查在以前未探索的过渡性“山谷”区域(~150公里)发生的小尺度不规则性。这些测量预计将支持这样一种理论，即需要强梯度才能使山谷中的等离子体在小范围内不稳定。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Earth's ionosphere is a mixture of neutral gas and charged particles. The ionosphere is generally broken out by layers, defined according to the wavelengths of the radiation most commonly absorbed. The E-region extends from 90-150 km and is ionized through X-ray and ultraviolet radiation. The F-region (150-600 km) is ionized by extreme ultraviolet radiation. Although waves and disturbances ("structuring") occur throughout the ionospheric medium ("plasma"), studies often focus on; either the E or F layer owing in part to limitations of experimental and theoretical; techniques employed. As a result, development of a unified view of ionospheric plasma structuring processes remains incomplete. This proposal will fill this gap by (1) developing a unified plasma instability theory applicable in the broad range of altitudes including the previously unexplored transitional valley region between the E and F region peaks and (2) observing the valley region with a radar that routinely receives returns from a broad range of altitudes. The proposed research leverages NSF assets and knowledge synthesis to contribute fundamentally to the theory of plasma instability and structuring. This knowledge is relevant to the communication and navigation industries, and therefore to society. The integrated theory will be incorporated into UAF plasma physics classes, that currently rely primarily on original journal publications rather than teaching modules. The proposal will also fund a new Ph.D. student.The proposed research will address the fundamental question of what combination of destabilizing and stabilizing factors results in the plasma perturbations growing in amplitude and producing ionospheric structures. The actual proposal activity consists of three interconnected projects: 1. Development a unified theory of ionospheric plasma instabilities including thermal, inertial, and gradient effects for arbitrary altitude and propagation; 2. Determination of the critical gradient length required to destabilize plasma in the non-isothermal case for arbitrary altitude; 3. Analysis of SuperDARN and ISR data to investigate small-scale irregularity occurrence in the previously unexplored transitional "valley" region (~150 km). These measurements are expected to provide support for a theory that strong gradients are required to make plasma unstable in the valley at small scales.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.