Collaborative Research: CEDAR--Large-Scale Characterization of the Sub-Auroral Polarization Stream and Its Impacts on the Ionosphere-Thermosphere System

在地磁暴期间，位于极光带赤道方向的电离层区域经常受到高速（1 km/s）等离子体流的纵向延伸通道的扰动，该通道被称为亚极光极化流（SAPS）。调查人员将分析当前太阳活动周期最大期的电离层扰动观测结果，目的是推导出一个综合的、基于观测的SAPS模型。该研究将检查SAPS流的开始、传播和衰减，并绘制总电子含量（TEC）观察到的伴随变化。将利用最近在Millstone Hill翻新的非相干散射雷达进行协调实验，以便将SAPS电场动态与电离层密度和化学变化联系起来，并测量它们对中性大气的影响。SAPS现象与强极向电场（50 mV/m）和电离层密度的深凹或低谷有关。SAPS被认为是一个反馈过程的结果，由此磁层起源的磁场对准电流在电离层槽中闭合，引发化学变化，进一步降低电离层密度，同时以保持电流连续性的方式增加电场。SAPS现象对电离层等离子体结构、电离层成分、等离子体不规则性的形成以及与中性大气的耦合具有重要影响。通过观测全面了解SAPS及其对热层的影响将是一个重大进展。SAPS传统上是用单一的雷达和卫星进行研究的，这导致了对了解SAPS作为一种多维的全球尺度现象的演变和影响的效用有限的表征。观测技术的最新进展从根本上改变了研究前景。在北美建造一个中纬度的SuperDARN雷达链，使SAPS等离子体流和电场的同时（~1分钟）视图在许多小时的MLT成为可能，而全球定位系统（GPS）接收器网络的扩展，使类似的时间尺度上的TEC的大陆尺度映射成为可能。初步比较表明，SAPS雷达观察到的是坐在一个增强的槽状密度功能，是由TEC映射。这项工作将导致开发一个适合于检验理论想法的SAPS现象学模型和开发风暴时间电离层模型，向更广泛的社区传播关于最近SAPS事件的全球范围信息，增加全球定位系统TEC数据库在科学研究中的应用，并指导科学家如何使用这些数据。此外，弗吉尼亚理工大学的一名研究生将接受新实验技术的培训，并将接受来自SuperDARN雷达、GPS和非相干散射雷达的数据合并的培训。

During geomagnetic storms the region of the ionosphere that lies just equatorward of the auroral zone is often perturbed by a longitudinally-extended channel of high-speed (1 km/s) plasma flow known as the sub-auroral polarization stream (SAPS). The investigators will analyze observations of ionospheric disturbances through the current period of solar cycle maximum with the aim of deriving a comprehensive, observationally based model of SAPS. The study will examine the onset, spread, and decay of SAPS flows and chart the accompanying changes observed in total electron content (TEC). Coordinated experiments will be conducted with the recently refurbished Incoherent Scatter Radar (ISR) at Millstone Hill in order to relate the SAPS electric field dynamics to changes in ionospheric density and chemistry and to gauge their effects on the neutral atmosphere. The SAPS phenomenon is associated with strong poleward-directed electric fields (50 mV/m) and a deep depression, or trough, in ionospheric densities. SAPS is believed to be a consequence of a feedback process whereby magnetic field-aligned current of magnetospheric origin closes across the ionospheric trough, eliciting chemical changes that further reduce the ionospheric density while increasing the electric field in a manner that maintains current continuity. The SAPS phenomenon has important consequences for structuring ionospheric plasma, ionospheric composition, formation of plasma irregularities, and coupling to the neutral atmosphere. The attainment of a comprehensive, observationally-based understanding of SAPS and its impacts on the thermosphere would be a major advance. SAPS has traditionally been studied with single radars and satellites, leading to characterizations that are limited in their utility for understanding the evolution and impacts of SAPS as a multi-dimensional, global-scale phenomenon. Recent advances in observational techniques have fundamentally altered the research landscape. The construction of a mid-latitude chain of SuperDARN radars in North America has made possible simultaneous (~1 min) views of SAPS plasma flows and electric fields across many hours of MLT while the expansion of the network of Global Positioning System (GPS) receivers has made possible continental-scale mapping of TEC on similar time scales. Initial comparisons indicate that the SAPS observed by the radars are seated in an enhanced trough-like density feature that is mapped by TEC. This work will lead to the development of a phenomenological model of SAPS that is suitable for testing theoretical ideas and the development of storm-time ionospheric models, the dissemination of global-scale information on recent SAPS events to the wider community, the increased application of the GPS TEC database to scientific research, and the instruction of scientists on the use of these data. In addition, a graduate student at Virginia Tech will be trained in the new experimental techniques and in the merging of data from the SuperDARN radars, GPS, and incoherent scatter radar.