Structure of the Earth's magnetosphere under Northward IMF conditions

地球磁场在太阳风中形成一个空腔，称为磁层;太阳风和磁层之间的相互作用最终决定了近地空间的动态，包括辐射带强度的变化和最壮观的极光（北方和南方极光）。这些相互作用的性质取决于与太阳风有关的磁场（行星际磁场，或IMF）的方向; IMF的"南"方向（与地球磁场相反）对许多磁层过程来说是优先的，但IMF方向变化很大，相比之下，人们对IMF北向条件下的磁层动态知之甚少。这方面的一个例子是地球磁层夜晚一侧的结构，它形成了一个延伸的磁尾。磁尾由夹在两个低密度区域（称为叶瓣）之间的等离子体片组成。在磁尾的教科书图片中，低纬度的“等离子体片”是热的，而叶中的等离子体非常冷，通常密度很低。然而，最近的一系列论文已经开始挑战这一范式，并发现在某些条件下，可以在叶中观察到异常热/高密度的等离子体，其中一些与令人困惑的“高纬度”极光发射有关，这些极光发射位于主极光区的极向。引起等离子体结构和高纬极光发射的机制是激烈争论的。该项目的目的是利用欧洲航天局集群使命等航天器提供的现场卫星数据，确定和解释与向北IMF有关的较复杂间隔期间磁尾的结构。这将开始与等离子体环境的统计分类，在向北IMF的条件下，并将导致与全球规模的极光数据集进行比较。我们希望这项工作将导致我们的理解的磁层的反应向北IMF条件的重大贡献。

The Earth's magnetic field forms a cavity in the solar wind called the magnetosphere; the interaction between the solar wind and the magnetosphere is ultimately responsible for the dynamics of near-Earth space, including variations in the intensity of the radiation belts and the most spectacular displays of the aurora (the northern and southern lights). The nature of these interactions depends on the orientation of the magnetic field associated with the solar wind (the interplanetary magnetic field, or IMF); a "southward" orientation of the IMF (opposite to the Earth's magnetic field) is preferential for many magnetospheric processes, but the IMF direction is highly variable, and the dynamics of the magnetosphere under northward IMF conditions are, in comparison, poorly understood. One example of this is the structure of the night side of the Earth's magnetosphere, which forms an extended magnetotail. The magnetotail consists of a plasma sheet sandwiched between two low density regions called the lobes. In the textbook picture of the magnetotail, the low latitude "plasma sheet" is hot, whereas the plasma in the lobes is very cold and usually low in density. However, a recent series of papers have begun to challenge this paradigm, and have found that under certain conditions uncharacteristically hotter/higher density plasma can be observed in the lobes, some of which are associated with perplexing "high latitude" auroral emissions which lie poleward of the main auroral region. The mechanisms causing both the plasma structure and the high latitude auroral emissions are hotly debated. The aim of this project is to use in situ satellite data from spacecraft such as the European Space Agency's Cluster mission to determine and explain the structure of the magnetotail during the more complex intervals associated with northward IMF. This will begin with a statistical classification of the plasma environment during northward IMF conditions, and will lead on to a comparison with global scale auroral datasets. We expect this work will lead to a significant contribution to our understanding of the magnetosphere's response to northward IMF conditions.