GEM: Subauroral Polarization Streams (SAPS): Stormtime Empirical Modeling, Database Generation and Comparison with Rice Convection Model-Equilibrium (RCM-E)

GEM：亚极光偏振流 (SAPS)：风暴时期经验建模、数据库生成以及与稻米对流模型平衡 (RCM-E) 的比较

• 批准号: 1502934
• 负责人: Phillip Anderson
• 金额: $ 27.04万
• 依托单位: University of Texas at Dallas
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-15 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1502934&HistoricalAwards=false
• 关键词: GEM; Subauroral; Polarization; Streams; SAPS

During space storms, electric fields and particle precipitation expand into mid-latitudes equatorward of the auroral oval. Electric fields, produced by the interaction of the magnetosphere with the onrushing solar wind ultimately are responsible for the auroral oval but they also cause high-energy electrons and ions to drift deep into the inner magnetosphere. The inner magnetosphere maps along magnetic field lines into the midlatitude ionosphere causing disturbances there. On the dusk side of the inner magnetosphere, the ions penetrate closer to the Earth (and thus to lower latitudes) than the electrons. The weak magnetic field-aligned currents associated with ion pressure gradients at high altitude in space surrounding the Earth close through the low-density sub-auroral ionosphere on the dusk side and in the process produce strong westward electric fields that set the subauroral ionospheric plasma in motion. The electric fields and the drifts they produce in the ionosphere are called subauroral polarization streams (SAPS). The resulting strong ionospheric electric fields map back out along magnetic field lines producing effects in the magnetosphere. This coupling is important in producing space weather disturbances. The proposal will develop an empirical model based on a suite of low-earth orbiting satellites that describes the global distribution of SAPS fields in the ionosphere as a function of solar and geophysical conditions. An important aspect of this work is an investigation of the feedback between the electrical conductance of the ionosphere and the SAPS evolution. The results will contribute to our ability to understand and predict the temporal evolution of space weather disturbances and their impacts on vulnerable technologies. Of particular importance, SAPS draw dense plasma from the dayside ionosphere in plumes up over the polar cap, which can disrupt GPS signals resulting in large errors in global positioning. A graduate student will be trained on the project at the University of Texas.The proposers will use 80 years of ionospheric observations covering different local time sectors taken by satellites in the Defense Meteorological Satellite, Dynamics Explorer, and Atmosphere Explorer Programs. These will be sorted by solar activity and geophysical parameters to construct the first empirical model of subauroral electric fields. The data will also be used in a superposed epoch analysis of magnetic storms to understand the evolution of the SAPS electric fields during different stages of the storm. The RCM-E model, which combines the Rice Convection Model (RCM) with an equilibrium (self-consistent) magnetic field model (E), is a physics-based model that will be used to explore the evolution of the SAPS and test how ionospheric conductance affects this evolution. Given the plasma distribution for each species along with the magnetic field and electric potential at the outer boundary of the inner magnetosphere at high altitude, and the electric conductance pattern in the ionosphere, RCM solves for the electrodynamics of the coupled magnetosphere-ionosphere system. An important new aspect of this work is the focus on the effects of ion-neutral coupling through the changes it produces in the imposed ionospheric conductance pattern (i.e., progressive decrease in subauroral density as the storm progresses).

在空间风暴期间，电场和粒子沉淀扩展到极光椭圆赤道方向的中纬度地区。由磁层与汹涌的太阳风相互作用产生的电场最终是极光椭圆的原因，但它们也导致高能电子和离子漂移到磁层内部深处。 内磁层沿着沿着磁场线映射到中纬度电离层，在那里引起扰动。 在内磁层的黄昏一侧，离子比电子更接近地球（因此也更接近低纬度）。与地球周围空间高空离子压力梯度相关的弱磁场定向电流靠近黄昏一侧的低密度极光下电离层，并在此过程中产生强大的向西电场，使极光下电离层等离子体运动。 在电离层中产生的电场及其漂移称为亚极光极化流（SAPS）。 由此产生的强电离层电场沿着沿着磁场线映射出来，在磁层中产生影响。 这种耦合在产生空间天气扰动方面很重要。该提案将在一套低地球轨道卫星的基础上开发一个经验模型，描述电离层中SAPS场的全球分布，作为太阳和地球物理条件的函数。 这项工作的一个重要方面是调查的电离层的电导和SAPS演变之间的反馈。 研究结果将有助于我们理解和预测空间气象扰动的时间演变及其对脆弱技术的影响。 特别重要的是，SAPS从极冠上空的向阳侧电离层中抽出密集的等离子体，这可能会干扰GPS信号，导致全球定位的巨大误差。 一名研究生将在得克萨斯大学接受关于该项目的培训，提议者将利用国防气象卫星、动力学探测器和大气探测器方案的卫星对电离层进行的80年观测，涵盖不同的当地时间段。 这些将根据太阳活动和地球物理参数进行排序，以构建第一个极光下电场的经验模型。 这些数据还将用于磁暴的叠加时代分析，以了解SAPS电场在磁暴不同阶段的演变。 RCM-E模型结合了Rice对流模型（RCM）和平衡（自洽）磁场模型（E），是一个基于物理的模型，将用于探索SAPS的演变，并测试电离层电导如何影响这种演变。给定每个物种的等离子体分布，沿着在高空内磁层外边界处的磁场和电势，以及电离层中的电导模式，RCM求解耦合磁层-电离层系统的电动力学。这项工作的一个重要的新方面是通过离子-中性耦合在外加电离层电导模式中产生的变化（即，随着风暴的发展，亚极光密度逐渐减少）。