Multi-Scale Experimental Investigations of Extreme Plasma Density Depletions in the Polar Ionosphere

这个项目将研究极地电离层中的一种现象，极地电离层是由于太阳辐射而高度电离的大气区域(海拔80至1000公里)，具有高浓度的带电粒子，即电子和离子。极洞是指在所谓的F区(150至500公里)不时出现的带电粒子(称为等离子体)的大量减少，据信在太阳辐射最低水平的太阳极小期发生得更频繁。这种空洞的形成与带电粒子与电磁场和大气环流的复杂相互作用有关，这在极地地区是独一无二的。了解极空穴的形成和内部结构填补了我们对这种相互作用理解的空白，有助于改进极地电离层的模型模拟。目前的太阳极小期为研究这一现象提供了一个很好的机会。这个项目将通过实验研究极洞以及等离子体对流在它们的形成和演化中的作用。极洞被认为是在非常缓慢的反太阳对流期间形成的，当时等离子体在没有任何电离源的情况下被捕获在统计极光椭圆形的正前方。同时，快速对流和等离子体的快速垂直输送也与极空穴的形成有关。结合位于北极帽的先进模块化非相干散射雷达(AMICR)的多点能力、ASTRA开发的变分同化工具IDA4D和超级双极光雷达网(SuperDARN)阵列的对流资料，将研究等离子体对流在极洞形成中的作用。极孔附近的密度被认为是非常有结构的。这项研究将探索极孔的内部结构，分析极孔内部和边缘存在的梯度，并评估它们对高频雷达后向散射的影响。最后，为了提高极帽地区电子密度条件的可预测性，这是建模中最困难的，将对太阳最小条件下的极帽密度进行统计分析。将利用IDA4D运行和从南北两极地区的COSMIC I任务收集的大量无线电掩星数据来研究极冠密度的变异性，以找出模型参数和数据导出参数具有最大差异的最有问题的时间段。这项工作将改善我们对太阳活动最小条件下极帽中等离子体损耗的了解。冬季和太阳活动最小期间的极冠是用于卫星通信、卫星导航、数据链路和空间态势感知等应用领域的电离层模型最成问题的区域之一。这项工作将通过直接调查极帽区域的最低极值和统计研究其可变性，提高对极帽区域电子密度进行建模的能力。该项目将支持一名职业生涯早期的女性研究人员，她在外联活动方面有着良好的记录，包括为老年人提供空间物理讲座，并开发www.sheisaursicist.com网站空间，通过出版关于女性物理学家职业道路的故事来促进和培养女性在物理学方面的成功。当一次新的采访发布后，该网站的独立浏览量达到了约2000次，激励着高中和本科的女学生选择物理作为她们的职业道路。这将有助于扩大代表不足的少数群体在STEM领域的参与。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。

This project will investigate a phenomenon called ‘polar holes’ in the polar ionosphere, which is a region of atmosphere (80 to 1000 km above sea level) that is highly ionized due to solar radiation, with high concentration of charged particles, i.e. electrons and ions. The polar hole refers to the large reduction of charged particles (called plasma) that appears from time to time in the so-called F-region (150 to 500 km) and is believed to happen more often during the solar minimum when the solar radiation is at its lowest level. The formation of such holes is related to the complex interactions of the charged particles with the electromagnetic field and atmospheric circulation that are unique in the polar region. Understanding the formation and internal structures of the polar holes fills the gap of our understanding of such interactions and helps improve model simulation of the polar ionosphere. The current solar minimum provides a good opportunity to study this phenomenon.This project will experimentally investigate the polar holes and the role of the plasma convection in their formation and evolution. Polar holes are believed to be formed during the periods of the very slow anti-sunward convection, when the plasma is trapped just poleward of the statistical auroral oval in the absence of any ionization sources. At the same time, fast convection with rapid vertical plasma transport has also been associated with the polar hole formation. Combining the multi-point capability of the Advanced Modular Incoherent Scatter Radar (AMISR) located in the northern polar cap, the state of art variational data assimilation tool IDA4D developed at ASTRA, and the convection data from the Super Dual Auroral Radar Network (SuperDARN) array, the role of plasma convection in the polar hole formation will be investigated. The density in the vicinity of the polar holes is thought to be very structured. This study will explore the polar hole internal structure, analyze the gradients that are present inside the polar hole and on its edges, and evaluate their effects on high-frequency radar backscatter. Finally, to improve the predictability of the electron density conditions in polar cap regions, which are most problematic for modeling, a statistical analysis of the polar cap density during the solar minimum conditions will be performed. Variability of the polar cap density will be investigated using IDA4D runs and large amounts of collected radio occultation data from COSMIC I mission in the northern and southern polar regions to find the most problematic time periods where the model parameters and data-derived parameters have the largest differences.The work will improve our knowledge of the plasma depletions in the polar cap during solar minimum conditions. The polar cap during the winter and during the solar minimum is one of the most problematic zones for the ionospheric models used in application areas, such as satellite communications, satellite-based navigation, data links, and space situational awareness. This work will improve the ability to model the electron density in the polar cap region by direct investigation of its lowest extremes and by statistical investigation of its variability. This project will support an early-career female researcher who has a strong track record of outreach activities, including delivering Space Physics lectures for senior people and developing the www.sheisaphysicist.com web space that promotes and cultivates the success of women in physics by publishing stories about the career path of female physicists. When a new interview is published, the website reaches ~2000 independent views, inspiring high-school and undergraduate female students to choose physics as their career path. This will contribute to broadening of participation of underrepresented minorities in STEM fields.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.