Collaborative Research: Investigations of the Mid-Latitude Ionosphere during Magnetic Disturbances: Observations, Modeling and Space Weather Impacts

研究人员将研究磁暴主阶段中纬度地区大尺度（几百公里）和小尺度（几十公里到几十米）等离子体的来源和演变。在大磁暴期间，在行星际磁场（IMF）南向的条件下，太阳风和磁层之间的相互作用导致第1区场向电流的变化，导致黎明到黄昏极帽势的突然增加。与朝黄昏至黎明方向的内磁层电场相关的2区场向电流不再能够屏蔽中纬度和赤道地区免受高纬度电场的影响。这导致一个电场从高纬度到中部和赤道电离层几乎瞬间穿透。提示穿透电场在白天至黄昏扇区呈东向，在午夜至黎明扇区呈西向。因此，这种穿透电场通过在白天增加层高度，从而增加等离子体密度，并增加黑暗中电离的衰减率，导致等离子体在整个等离子体层和电离层中的显著重新分布。最近，美国国家科学基金会资助的几个美国经度和同化模型仪器阵列的扩展，首次使这种合作研究成为可能。大尺度等离子体密度的行为最好通过跟踪GPS测量的总电子含量（TEC）来跟踪，使用一个新形成的阵列，从赤道地区穿过加勒比海进入美国大陆，以确定低纬度对中纬度增强的贡献，即风暴增强密度（SED）。现在有各种资料同化模式可用于模拟SED的产生，并测试赤道对这种中纬度特征的贡献程度，从而形成这种耦合现象的气候学。这项合作研究将首次尝试确定低纬度TEC对美国经度中纬度地区的贡献，以了解SED中的电离源，确定数百公里到十米尺度的二维结构和速度，并确定TEC梯度和相位闪烁对天基导航系统的影响。该研究对于更好地实现支持民用和商用航空的广域增强系统（WAAS）也具有重要意义。

The investigators will study the source and evolution of the large scale (several hundred kms) and small scale (tens-of-km to tens-of-m) plasma at mid-latitudes during the main phase of magnetic storms. During major magnetic storms, the interaction between the solar wind and the magnetosphere under interplanetary magnetic field (IMF) southward conditions causes a change in the region 1 field-aligned currents leading to a sudden increase in the dawn-to-dusk polar cap potential. The region 2 field-aligned currents associated with an inner magnetospheric electric field directed in the dusk-to-dawn direction are no longer able to shield the mid- and equatorial latitudes from high-latitude electric fields. This results in a near-instantaneous penetration of an electric field from high latitude to the middle and the equatorial ionosphere. The prompt penetration electric field is eastward during the daytime to dusk sector and westward in the midnight to dawn sector. Thus this penetration electric field leads to a significant re-distribution of plasma throughout the plasmasphere and ionosphere by enhancing the layer height, and thereby the plasma density, during daylight hours and increasing the decay rates of ionization in darkness. The recent extension of several NSF-funded instrument arrays at American longitudes and assimilation models have made this collaborative research possible for the first time. The large scale plasma density behavior is best tracked by following the GPS measured total electron content (TEC) from equatorial regions using a newly-formed array through the Caribbean and into the continental US to determine the low latitude contribution to mid-latitude enhancements known as storm enhanced density (SED). A variety of data-assimilation models are now available to model the generation of the SED and test the extent of the equatorial contribution to this mid-latitude feature, thereby developing a climatology of such coupled phenomena. This collaborative research will be the first attempt to determine the contribution of the low latitude TEC on mid-latitudes at American longitudes to understand the source of ionization in the SED, to determine the 2D structure and velocity of hundreds of km scales to decameters and to determine the impact of TEC gradients and phase scintillations on space-based navigation systems. This research is also important for better implementation of the Wide-Area Augmentation System (WAAS), which supports civilian and commercial aviation.