Ground-based Detection of Ionospheric Density Modulations due to Alfven waves using AMISR and Ground-Based Optics at Poker Flat, Alaska

对于在极光中观测到的高度动态和非常小尺度的结构，一种新兴的解释是，它是电离层密度调制和共振阿尔芬波之间反馈的结果。该模型是建立在电离层Alfven谐振器（IAR）和电离层反馈不稳定性（IFI）两种机制结合的基础上的。目前还不可能对该模型进行明确的观测证实。这是一个为期四年的项目，旨在为电离层中的这些机制提供前所未有的实验证据。它将利用位于Poker Flat Rocket Range （PFRR）的先进模块化非相干散射雷达（AMISR）的先进能力来克服现有实验数据中普遍存在的时空模糊性。具体来说，AMISR的全脉冲光束控制能力以及先进的信号处理技术将用于获得离子速度和电子密度扰动的垂直和水平分辨频域测量，奈奎斯特频率为100 Hz。超级雷达网络将提供更大空间尺度上离子漂移速度的额外测量，PFRR的视频速率增强成像将用于确定与Alfvenic活动相关的快速发射极光形式的形态。观测结果将与调整到普遍条件下的IAR/IFI模拟进行比较，以测试与阿尔芬波的关联。该研究项目将重点回答以下三个具体的科学问题：在频域中观察到的周期性离子速度和密度调制的垂直和水平分布是什么，这些是否与IAR/IFI模型兼容？导电电离层的薄板模型是否显著地扭曲了IFI的模型？如果不存在IAR/IFI模型签名，哪些模型假设没有实现？此外，除了回答这些重要的科学问题外，该项目还具有重要的更广泛的影响。它将为AMISR设施开发和测试先进技术，并将演示其作为覆盖极低频频率范围的等离子体结构频谱分析仪的用途。此外，它代表了跨学科科学的一个很好的例子：用电离层群落的技术和详细观测来检验磁层群落中流行的理论模型。

An emerging explanation for the highly dynamic and very small-scale structure observed in the aurora is that it results from feedback between ionospheric density modulations and resonant Alfven waves. This model is founded on the combination of two mechanisms: the ionospheric Alfven resonator (IAR) and the ionospheric feedback instability (IFI). Definitive observational confirmation of the model has not yet been possible. This is a four-year project to provide unprecedented experimental evidence related to these mechanisms in the ionosphere. It will utilize the advanced capabilities of the Advanced Modular Incoherent Scatter Radar (AMISR) at the Poker Flat Rocket Range (PFRR) to overcome the space-time ambiguities prevalent in existing experimental data. Specifically, the full pulse-by-pulse beam steering capability of AMISR together with advanced signal processing techniques will be used to obtain vertically and horizontally resolved frequency domain measurements of perturbations in ion velocity and electron density, with a Nyquist frequency of 100 Hz. Additional measurements of ion drift velocities at a larger spatial scale will be provided by the SuperDARN radar network and video rate intensified imaging at PFRR will be used to determine the morphology of prompt emitting auroral forms associated with Alfvenic activity. The observations will be compared with IAR/IFI simulations tuned to the prevailing conditions, in order to test for association with Alfven waves. The research project will focus on answering the following three specific science questions: What are the observed vertical and horizontal profiles of periodic ion velocity and density modulations in the frequency domain, and are these compatible with the IAR/IFI model? Does the thin slab model of the conducting ionosphere significantly distort modeling of the IFI? In the event that the IAR/IFI model signatures are not present, which of the model assumptions are not realized?In addition, to answering these important science questions, the project has significant broader impacts as well. It will develop and test advanced techniques for the AMISR facility and will demonstrate its use as a plasma structure spectrum analyzer, covering the ELF frequency range. In addition, it represents a good example of interdisciplinary science: testing a theoretical model popular in the magnetospheric community with the techniques and detailed observations of the ionospheric community.