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

职业：地球弓形激波上游的动力学现象及其地磁效应

• 批准号: 1352669
• 负责人: Hui Zhang
• 金额: $ 65.06万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-15 至 2023-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1352669&HistoricalAwards=false
• 关键词: CAREER; Kinetic; Phenomena; Upstream; Earth

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.

该项目的重点是更好地理解太阳能驱动地球附近空间天气干扰的方式。地球受到太阳风的直接影响，其磁场延伸至高度，并导致太阳风在其周围偏转。当地球的磁场通过称为磁合并的过程连接到太阳的磁场时，一些太阳能进入接近地球的空间。 太阳风与地球磁层之间的相互作用加速了等离子体颗粒，使能量足以威胁到航天器电子和宇航员健康，此外，还会在高层大气中产生大气中的大型电流，从而破坏地球表面上的电力网格。 为了预测太空天气，因此提供了一些警告以实施调解策略，重要的是要了解实际击中磁层的太阳风中的条件。 出现并发症是因为要获得足够的预测预测为有价值，因此必须测量地球上游的太阳风。 但是，这种不受干扰的太阳风并不是最终触发太空袭击的原因。 取而代之的是，在到达磁层之前，太阳风被修饰，因为它形成弓形冲击和一层冲击和加热的血浆（称为磁石）。 结果，重要的是要能够将对地球上游的不受干扰的太阳风与实际到达的太阳风相关联，然后与所产生的太空风暴相关联。 这项研究的结果将用于研究生和本科教育目的，并将被广泛传播。 从长远的角度来看，更好地了解太阳能风层层的相互作用可能会改善对社会价值的天气预测的改善，并将与行星和天体物理等离子体环境的研究有关。 相关的太空天气主题将在各个场所的公共宣传活动中展出。 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)弓冲击的上游。 尽管已经观察到这些瞬变数十年，但是产生它们的基本物理机制，如何修改太阳能磁层的相互作用以及导致近地球空间内的签名类型的类型仍不清楚。由于太阳风与磁层的相互作用会产生瞬变，并反馈瞬态以修改太阳能磁层的相互作用，因此这些特征必须是作为连接系统的研究，以识别潜在的机制。 本工作将使用观测值来识别各种类型的太阳风瞬变以及它们所产生的条件，然后使用模拟来识别基本的物理机制。这种整体方法有望产生重要的进步。