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

在空间风暴期间，电场和粒子降水扩展到极光椭圆赤道的中纬度地区。磁场是由磁层与冲来的太阳风相互作用产生的，最终导致了极光椭圆形，但它们也导致高能电子和离子深入到内部磁层。内部磁层沿着磁力线映射到中纬度电离层，在那里造成干扰。在磁层内侧的黄昏面，离子比电子更接近地球（因此更低纬度）。弱磁场排列的电流与地球周围高海拔空间的离子压力梯度有关，在黄昏时通过低密度的亚极光电离层，并在此过程中产生强大的西向电场，使亚极光电离层等离子体运动起来。电离层中产生的电场和漂移被称为亚极光极化流（SAPS）。由此产生的强电离层电场沿着磁力线向外映射，在磁层中产生影响。这种耦合在产生空间天气干扰方面是重要的。该提案将开发一个基于一套低地球轨道卫星的经验模型，该模型将电离层中SAPS场的全球分布描述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电离层电导与SAPS演化之间的反馈关系的研究。这些结果将有助于我们理解和预测空间天气干扰的时间演变及其对脆弱技术的影响。特别重要的是，SAPS从白天的电离层吸收密集的等离子体，形成羽状上升到极帽上方，这可能会干扰GPS信号，导致全球定位的巨大误差。一名研究生将在德克萨斯大学接受该项目的培训。提议者将使用80年的电离层观测数据，涵盖国防气象卫星、动力探测器和大气探测器计划中卫星所拍摄的不同当地时间部门。这些数据将根据太阳活动和地球物理参数进行分类，以构建第一个亚极光电场的经验模型。这些数据还将用于磁暴的叠加年代分析，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。考虑到各物种的等离子体分布、高海拔内磁层外边界的磁场和电势以及电离层内的电导图，RCM解决了磁层-电离层耦合系统的电动力学问题。这项工作的一个重要的新方面是关注离子-中性耦合的影响，通过它在强加的电离层电导模式中产生的变化（即，随着风暴的进展，亚极光密度逐渐减少）。

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).