CAREER: Kinetic Phenomena Upstream from the Earth's Bow Shock and Their Geomagnetic Effects

这个项目的重点是更好地了解太阳风驱动地球附近空间天气扰动的方式。地球的磁场延伸到高海拔地区，导致太阳风在地球周围偏转，从而保护地球免受太阳风的直接影响。当地球？当太阳风的磁场通过一种叫做磁合并的过程与太阳的磁场相连时，一些太阳风的能量进入了近地空间。太阳风和地球磁层之间的相互作用将等离子体粒子加速到足以威胁航天器电子设备和宇航员健康的能量，此外，还会在高层大气中产生兆安培电流，从而破坏地球表面的电网。为了预测空间天气，从而为实施调解策略提供一些警告，了解太阳风实际撞击磁层的条件非常重要。复杂的情况出现了，因为为了获得足够的提前时间使预测有价值，太阳风必须在地球上游测量。然而，这种未受干扰的太阳风并不是最终引发太空风暴的原因。相反，太阳风在到达磁层之前会形成弓形激波和一层激波和加热的等离子体（称为磁鞘）。因此，重要的是能够将观测到的地球上游未受干扰的太阳风与实际到达的太阳风以及产生的太空风暴联系起来。这项研究的结果将用于研究生和本科生的教育目的，并将广泛传播。从更长远的角度来看，对太阳风-磁层相互作用的更好理解将可能导致对社会有价值的空间天气预报的改进，并将与行星和天体物理等离子体环境的研究相关。相关的空间天气主题将在不同场地的公众外展活动中呈现。与地球物理研究所的公共信息和外联教育办公室的伙伴关系将大大增加外联活动的范围，而不仅仅是提议小组。观测表明，一群太阳风离子从弓形激波中反射回来，返回太阳，并与入射太阳风非线性地相互作用，在弓形激波上游产生各种瞬态特征（即热流异常、前激波空腔和密度洞）。虽然这些瞬变现象已经被观察了几十年，但产生它们的潜在物理机制，它们如何改变太阳风-磁层相互作用，以及在近地空间产生的特征类型仍然不为人所知。由于太阳风与磁层的相互作用产生了瞬变和瞬变反馈，从而改变了太阳风与磁层的相互作用，因此必须将这些特征作为一个相互联系的系统来研究，以确定其潜在的机制。目前的工作将使用观测来确定各种类型的太阳风瞬变，以及它们产生的条件，然后使用模拟来确定潜在的物理机制。这种整体的方法有望产生重要的进展。

This project is focused on better understanding of the ways in which solar wind energy drives space weather disturbances near Earth. The Earth is protected from the direct impact of the solar wind by its magnetic field that extends out to high altitudes and causes the solar wind to be deflected around it. When the Earth?s magnetic field becomes connected to the Sun's magnetic field through a process called magnetic merging, some of the solar wind energy enters near-Earth space. The interaction between the solar wind and the Earth's magnetosphere accelerates plasma particles to energies high enough to threaten spacecraft electronics and astronaut health, and in addition, creates mega-ampere electric currents in the upper atmosphere that can disrupt power grids on the Earth's surface. To predict space weather and thus provide some warning to implement mediation strategies, it is important to understand the conditions in the solar wind that actually hit the magnetosphere. Complications arise because to get sufficient lead-time for the prediction to be of value, the solar wind must be measured upstream of the Earth. However, this undisturbed solar wind is not what eventually triggers the space storming. Instead the solar wind is modified as it forms a bow shock and a layer of shocked and heated plasma (called the magnetosheath) before arriving at the magnetosphere. As a result, it is important to be able to relate observations of the undisturbed solar wind far upstream of the Earth with the solar wind that actually arrives and then to the space storm that is produced. The results of this study will be used for graduate and undergraduate education purposes, and will be disseminated widely. Taking a longer-range perspective, a better understanding of the solar wind-magnetosphere interaction will likely result in improvements to space weather forecasting of value to society and will be relevant to the study of planetary and astrophysical plasma environments. Related space weather topics will be featured in public outreach activities in various venues. A partnership with the Public Information and Outreach Education Office at the Geophysical Institute will significantly increase the scope of the outreach activities beyond the proposing team alone.Observations indicate that a population of solar wind ions reflects from the bow shock, travels back toward the Sun and interacts non-linearly with the incoming solar wind producing a variety of transient features (i.e., hot flow anomalies, foreshock cavitons, and density holes) upstream of the bow shock. Though these transients have been observed for decades, the underlying physical mechanisms that produce them, how they modify the solar wind-magnetosphere interaction, and the types of signatures that result within near-Earth space are still not understood. Since the interaction of the solar wind with the magnetosphere produces the transients and the transients feed back to modify the solar wind-magnetosphere interaction, these features must be studies as a connected system in order to identify the underlying mechanisms. The present work will use observations to identify the various types of solar wind transients, and the conditions under which they are produced, and then use simulations to identify the underlying physical mechanisms. This holistic approach is expected to produce important advances.