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，电场和粒子降水向极光椭圆形的赤道方向扩展到中纬度。磁层与汹涌的太阳风相互作用产生的电场最终是造成极光椭圆形的原因，但它们也导致高能电子和离子漂移到磁层内部深处。内部磁层沿着磁力线映射到中纬度电离层，造成那里的扰动。在内部磁层的黄昏一侧，离子比电子更接近地球(从而到达更低的纬度)。与地球周围空间高空离子压力梯度有关的弱磁场对准电流通过黄昏一侧的低密度亚极光电离层关闭，并在此过程中产生向西的强电场，使亚极光电离层等离子体启动。在电离层中产生的电场和漂移称为亚极光极化流(SAPS)。由此产生的强大电离层电场沿着磁力线映射回来，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。该提案将在一套近地轨道卫星的基础上开发一个经验模型，描述作为太阳和地球物理条件函数的电离层SAPS场的全球分布。这项工作的一个重要方面是研究电离层电导与SAPS演化之间的反馈。这些结果将有助于我们理解和预测空间天气扰动的时间演变及其对脆弱技术的影响。特别重要的是，SAPS在极冠上方的羽状物中从日侧电离层吸收高密度等离子体，这可能会扰乱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。计划者将使用国防气象卫星、动力学探测器和大气探测器计划中卫星拍摄的覆盖不同当地时间段的80年电离层观测数据。这些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经验模型。这些数据还将用于磁暴的叠加历元分析，以了解风暴不同阶段SAPS电场的演变。RCM-E模型结合了赖斯对流模型(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的演化并测试电离层电导如何影响这种演化。给定每种物质的等离子体分布，以及高海拔内磁层外边界的磁场和电势，以及电离层中的电导模式，RCM求解了磁层-电离层耦合系统的电动力学。这项工作的一个重要新方面是侧重于离子-中性耦合通过其在施加的电离层电导模式中产生的变化所产生的影响(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).