Spatiotemporal variations of electromagnetic charachteristics of equatorial plasma depletions

Swarm卫星新的现场观测揭示了有趣的电离层等离子体密度结构和电磁特性。这些发生在日落后在电离层F区高度（200至1500公里）的赤道等离子体耗尽（EPD）。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建模预测的等离子体耗尽特征。我们可以观察到，与血浆耗尽相关的场向电流主要沿半球流动（从一个半球到另一个半球），而不是像理论预期的那样对称地远离和朝向赤道。我们还报道了等离子体损耗的坡印廷通量的第一个观测证据。同样，令人惊讶的是，坡印廷通量被发现主要是半球间的。此外，半球间坡印廷通量和场向电流方向显示出显着的季节性和纵向依赖性，我们涉及到电离层电导率的季节性影响。在我们项目的第二阶段，我们希望通过（1）分析扩展的数据集，以便更好地覆盖季节和当地时间，以及（2）通过基于物理的模型添加模拟，来提高我们对基础物理的理解。此外，我们将在赤道Jicamarca天文台使用新安装的雷达模式（中等非相干散射雷达（ISR）长期运行），将日落前和日落期间的等离子体漂移与不同季节的等离子体耗尽的Swarm观测结果相关联。ISR运行将提供更大规模的EPD动态图片，支持对Swarm现场测量结果的解释。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EPD功能。为此，我们将通过Swarm对高节奏电子密度和磁场记录进行频域分析，并将其与GPS观测结果相关联，以确定导致振荡的散射条件。因此，我们充分利用了Swarm使命的多仪器能力。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见解，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。关于EPD的知识也与精确的地核和岩石圈磁场建模有关，因为与EPD有关的电流会产生系统性偏差。

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.