RAPID: Novel Experimental Quantification of Energetic Electron Properties During Ionospheric Modification

这一为期一年的快速项目旨在对高功率电离层改造过程中产生的电子的能量分布提供前所未有的经验约束，以此作为促进对电子加速过程的了解的一种手段。高功率高频无线电波发射机是地面电离层等离子体基础物理实验研究的重要工具。三个高频加热设施(HAARP、EISCAT和阿雷西博天文台)已经证明有能力诱导头顶等离子体密度接近太阳光致电离产生的密度，从而能够对高能电子的产生、加速和传输进行经验研究。然而，尽管在过去的几十年里进行了大量的实验，但在电离层修改过程中导致电子加速的物理机制仍然没有得到解决。为了解决这一问题，本项目采用了一种新的方法，即由阿雷西博天文台的非相干散射雷达(ISR)进行等离子体线和离子线探测的结合。这是同类仪器中最灵敏的，加上对氧原子在844.6 nm和630.0 nm发射的光学气辉的被动测量。研究活动将利用阿雷西博天文台和附近库莱布拉岛现场的几乎所有设施和PI拥有的光学仪器，进行前所未有的协调努力。与过去对电离层修改过程中电子加速的研究不同，本项目期间的研究分析将纳入热层氧密度的一致经验估计，PI将从氧844.6 nm发射线亮度的校准测量中得出。这项研究工作将由职业生涯早期的女性PI领导。这一快速项目的研究议程支持AGS司在发现、学习、多样性和跨学科研究方面的战略目标。旨在获得对电离层修改过程中高能电子加速的前所未有的经验约束的研究工作的结果将对管理弱磁化等离子体物理的基本理论产生深远的影响。例如，未来对等离子体层中俯仰角散射的电子能量损失的研究将从这项工作的结果中受益。尽管推进电离层等离子体物理是这项工作的主要焦点，但PI仔细的实验设计也将对氧844.6 nm发射线通过O+辐射复合激发的速率产生关键的限制。此外，计划在这一近红外波长以及氧630.0纳米发射线上进行天文校准，将为今后的活动提供一种期待已久的交叉校准设施校准源的手段。最后，新的氧844.6 nm发射线光度计可以很容易地配置为进行常规的被动测量，供社区使用。即使在没有高频电离层加热的情况下，校准的氧844.6 nm发射线数据也为热层氧传感提供了一种手段。这一能力目前在任何其他ISR设施中都不可能实现，它使得对离子-中性耦合的关键研究成为可能，这是推进高层大气基于物理的模型所必需的。。

This one-year RAPID project is aimed at providing unprecedented empirical constraints on the energy distribution of electrons generated during high-power ionospheric modification as a means of advancing understanding of electron acceleration processes. High-power, high-frequency (HF) radio wave transmitters are an important tool for the experimental investigation of fundamental plasma physics in the terrestrial ionosphere. Three HF heating facilities (HAARP, EISCAT, and Arecibo Observatory) have demonstrated the ability to induce overhead plasma densities approaching those created by solar photoionization, thereby enabling empirical studies of energetic electron production, acceleration and transport. Despite numerous experiments over the past several decades, however, the physical mechanisms responsible for electron acceleration during ionospheric modification remain unsettled. In order to tackle this problem, this project adopts a novel approach that involves the combination of plasma-line and ion-line detection by the Arecibo Observatory incoherent scatter radar (ISR). This is the most sensitive instrument of its kind, together with passive measurement of optical airglow emitted by Oxygen atoms at 844.6 nm and 630.0 nm. The research campaign will utilize nearly all of the facility and the PI-owned optical instrumentation on site at the Arecibo Observatory and at the nearby Culebra island in an unprecedentedly coordinated effort. Unlike past investigations of electron acceleration during ionospheric modification, the research analysis during this project will incorporate coincident empirical estimates of thermospheric Oxygen density, which the PI will derive from calibrated measurements of the Oxygen 844.6 nm emission line brightness. This research effort will be led by an early-career, female PI. The research agenda of this RAPID project supports the Strategic Goals of the AGS Division in discovery, learning, diversity, and interdisciplinary research The results from the intended research effort to obtain unprecedented empirical constraints on energetic electron acceleration during ionospheric modification will have far-reaching impact on fundamental theories governing the physics of weakly magnetized plasmas. Future investigations of electron energy loss from pitch angle scattering in the plasmasphere, for example, will benefit from the results of this work. Although advancing ionospheric plasma physics is the primary focus of the effort, the careful experimental design by the PI will also yield crucial constraints on the rate of Oxygen 844.6 nm emission line excitation via O+ radiative recombination. Moreover, the intended implementation of astronomical calibration at this near-infrared wavelength as well as at the Oxygen 630.0 nm emission line will provide a long-awaited means of cross-calibrating the facility calibration sources for future campaigns. Finally, the new Oxygen 844.6 nm emission line photometer can easily be configured to conduct routine passive measurements for community use. Even in the absence of HF ionospheric heating, the calibrated Oxygen 844.6 nm emission line data provide a means for Thermospheric Oxygen sensing. This capability, which currently is not possible at any other ISR facility, enables crucial investigations of ion-neutral coupling which are needed to advance physics-based models of the upper atmosphere. .