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相期间中纬度大尺度(数百公里)和小尺度(数十公里至数十米)等离子体的来源和演化。在重大磁暴期间，太阳风和磁层在行星际磁场(IMF)向南条件下的相互作用导致区域1场向电流的变化，从而导致从黎明到黄昏的极帽电位突然增加。与黄昏到黎明方向的磁层内电场有关的区域2场向电流不再能够保护中纬度和赤道地区免受高纬度电场的影响。这导致电场从高纬度几乎瞬间穿透到中层和赤道电离层。瞬变穿透电场白天至黄昏时段向东移动，午夜至黎明时段向西移动。因此，这种穿透电场通过在白天增加等离子体层高度，从而增加等离子体密度，并在黑暗中增加电离的衰减率，从而导致等离子体在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仪器阵列在美国经度和同化模型上的扩展使这一合作研究首次成为可能。跟踪大尺度等离子体密度行为的最好方法是跟踪来自赤道地区的GPS测量的总电子含量(TEC)，使用一个新形成的阵列穿过加勒比海并进入美国大陆，以确定低纬度对中纬度增强的贡献，即所谓的风暴增强密度(SED)。现在有各种数据同化模式可用于模拟SED的产生，并测试赤道对这一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TEC对美洲经度中纬度的贡献，以了解SED中的电离源，确定数百公里尺度到分米的二维结构和速度，并确定TEC梯度和相位闪烁对天基导航系统的影响。这项研究对于更好地实施支持民用和商业航空的广域增强系统(WAAS)也很重要。

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.