Spatiotemporal variations of electromagnetic charachteristics of equatorial plasma depletions

Swarm卫星的新原位观测揭示了电离层等离子体密度结构和电磁特性。这些现象发生在日落后电离层F区高度（200至1500公里）发生的赤道等离子体消耗（EPDs）。在我们项目的第一阶段，我们从Swarm卫星观测中发现了迄今为止尚未通过物理模型预测的等离子体消耗特征。我们可以观察到，与等离子体消耗相关的场对准电流主要是在半球间流动（从一个半球到另一个半球），而不是像理论所期望的那样，对称地远离和朝向赤道。我们还报道了第一个观测到的坡印廷等离子体耗竭通量的证据。再一次，令人惊讶的是，波印廷通量被发现主要是半球间的。此外，半球间坡印亭通量和场向电流方向表现出明显的季节和纵向依赖性，这与电离层电导率的季节效应有关。在我们项目的第二阶段，我们希望通过(1)分析一个扩展的数据集，允许更好的季节和当地时间覆盖(2)添加基于物理模型的模拟来提高我们对基础物理的理解。此外，我们将使用赤道Jicamarca天文台新安装的雷达模式（中频非相干散射雷达（ISR）长距离运行），将日落前和日落时的等离子体漂移与不同季节等离子体消耗的Swarm观测相关联。ISR运行将提供更大规模的EPD动态图像，支持对Swarm原位测量的解释。该项目的另一个目的是调查与Swarm卫星上GPS导航信号中断有关的环保署特征。为此，我们将对Swarm的高节奏电子密度和磁场记录进行频域分析，并将其与GPS观测结果联系起来，以确定引起闪烁的散射条件。因此，我们充分利用了蜂群任务的多仪器能力。通过使用多参数数据集解决上述问题，我们期望对高层大气的电磁机制有新的、基本的认识，并在我们描述和预测epd的能力方面取得重大进展，最后，减轻它们对基于无线电波的技术基础设施（如GPS）的影响。由于与epd相关的电流会产生系统偏差，因此epd知识也与精确的地核和岩石圈磁场建模相关。

New in situ observations by the Swarm satellites are revealing intriguing ionospheric plasma density structures and electromagnetic properties. These occur for equatorial plasma depletions (EPDs) that evolve after sunset at ionospheric F region altitudes (200 to 1500 km). In the first phase of our project, we discovered features of the plasma depletions from Swarm satellite observations that have not been predicted by physical modelling so far. We could observe that plasma depletion related field-aligned currents are mainly flowing interhemispherically (from one hemisphere to the other) rather than symmetrically away from and towards the equator, as was expected from theory. We also reported the first observational evidence of the Poynting flux of plasma-depletions. Again, surprisingly, the Poynting flux is found to be mainly interhemispheric. Furthermore, the interhemispheric Poynting flux and field-aligned current directions shows a significant seasonal and longitudinal dependence, which we relate to the seasonal effects of ionospheric conductivity. In the second phase of our project, we want to improve our understanding of the underlying physics by (1) analysing an extended data set allowing for a better seasonal and local time coverage and (2) adding simulations by physics-based models. Additionally, we will use a newly installed radar mode (medium incoherent scatter radar (ISR) long runs) at the equatorial Jicamarca observatory to correlate plasma drifts before and during sunset hours with Swarm observations of plasma depletions during different seasons. ISR runs will provide larger-scale pictures of the EPD dynamics supporting the interpretation of the Swarm in situ measurements. Another aim of this project is the investigation of EPD features related to outages of GPS navigation signals on board the Swarm satellites. To this end, we will perform a frequency domain analysis of high-cadence electron density and magnetic field records by Swarm and relate it to GPS observations to identify the scattering conditions that cause scintillations. Thus, we make full use of the multi-instrument capabilities of the Swarm mission. By addressing the aforementioned questions with multiple parameter data sets, we expect new, fundamental insights into the electromagnetic mechanisms of the upper atmosphere as well as significant advances in our ability to describe and forecast EPDs and, finally, to mitigate their impact on radio wave based technological infrastructure like GPS. Knowledge on EPDs is also relevant for precise core and lithospheric magnetic field modelling since EPD-related electric currents produce systematic biases.