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

合作研究：CEDAR——次极光偏振流的大规模表征及其对电离层-热层系统的影响

• 批准号: 1243070
• 负责人: J Michael Ruohoniemi
• 金额: $ 29.81万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1243070&HistoricalAwards=false
• 关键词: Collaborative; Research; CEDAR; Large; Scale

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.

在地磁风暴期间，高速（1 km/s）等离子体流动的纵向扩展的通道通常会扰动高速延伸的电离区域的电离层区域。研究人员将通过当前太阳周期最大时期分析电离层干扰的观察结果，目的是推导一种基于观察的SAP的全面模型。 该研究将检查SAPS流的发作，扩散和衰减，并绘制总电子含量（TEC）中观察到的随附变化。 为了将SAPS电场动力学与电离层密度和化学的变化相关联，将使用最近翻新的不相干散射雷达（ISR）进行协调实验，并评估其对中性气氛的影响。 SAPS现象与电离层密度的强极导向电场（50 mV/m）以及深层凹陷或槽有关。据信SAPS是反馈过程的结果，磁层起源的磁场对流电流在电离层槽上关闭，从而引发了化学变化，从而进一步降低了电离层密度，同时以保持电流连续性的方式增加电场。 SAP现象对结构电离层等离子体，电离层组成，等离子体不规则的形成以及与中性气氛耦合有重要后果。获得对SAP的全面，基于观察的理解及其对热圈的影响将是一个重大进步。 传统上，SAPS是用单个雷达和卫星研究的，导致其特征限制了其效用，以理解SAPS作为多维，全球规模的现象的演变和影响。观察技术的最新进展从根本上改变了研究格局。北美超级雷达的中纬度链的构建使得SAPS等离子体流量和电场在许多小时的MLT中的同时（〜1分钟）的观点成为可能，而全球定位系统（GPS）接收器网络的扩展使TEC在相似的时间尺度上的大陆尺度映射成为可能。初始比较表明，雷达观察到的SAP位于由TEC映射的增强的槽状密度特征中。这项工作将导致SAP的现象学模型的发展，该模型适用于测试理论思想和风暴时间电离层模型的发展，将有关SAPS事件的全球尺度信息传播给更广泛的社区，GPS TEC数据库在科学研究中的应用增加，以及对这些数据使用的科学家的指导。此外，弗吉尼亚理工大学的研究生将接受新的实验技术以及超级雷达，GPS和不连贯性散点雷达的数据合并。