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首页> 外文学位 >The storm time evolution in the night side high altitude field aligned wave Poynting flux and its relation to low altitude downward electron kinetic energy flux at low latitudes.
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The storm time evolution in the night side high altitude field aligned wave Poynting flux and its relation to low altitude downward electron kinetic energy flux at low latitudes.

机译：夜间高空场对准波Poynting通量的风暴时间演变及其与低纬度低空下行电子动能通量的关系。

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摘要

In this thesis we investigate the evolution of the wave and large scale Poynting flux on earth's night side at altitudes from the auroral acceleration regions to the near earth tail over the course of major geomagnetic storms. Specifically, we are examining the field aligned components of the Poynting flux which carries energy from the tail into the auroral acceleration regions and to the ionosphere, and the down going field aligned electron kinetic energy flux. During major storm Poynting flux, over the range of observed time scales (from 6-180 seconds, and 600 -7200 seconds) intensify significantly (between one and three orders of magnitude), even down to low latitudes (≤ 65o invariant latitude). Concurrently, over the same range of latitudes, but at low altitudes, the downward electron kinetic energy flux enhances by at least an order of magnitude. The wave Poynting flux is thus shown to be a significant energy transport mechanism at low latitudes during storms, which provides strong evidence that Alfven waves can be an important mechanism for auroral electron acceleration at low latitudes. This result is important, in part because low latitudes are on field lines mapping to the inner magnetosphere, and the nature of the energy transport processes associated with the near tail and inner magnetosphere are not yet fully understood. Most previous research on the Alfven wave powered aurora focused on the higher latitude regions of the auroral zone and plasma sheet boundary layer. Prior studies were also conducted with either localized spacecraft conjunctions or with long term statistical compilations. The study presented herein is the first to examine the wave Poynting flux evolution over the course of major storms, from pre-storm, main phase, and recovery phase, from a high altitude standpoint on an orbit by orbit basis and to compare this to the low altitude electron kinetic energy flux. We find that the latitudinal evolution of the intensities of the high altitude wave Poynting flux and low altitude electron kinetic energy flux correspond well with each other. This suggests that there is a generative relation between them that exists over the course of the storm; i.e. either some of the electrons are accelerated by the waves or the electrons and waves are both produced by some third mechanism. A quantitative comparisons of the mapped wave Poynting flux to auroral images and to integrated electron kinetic energy flux, suggests the Poynting flux carries anywhere from ~5% to well over 100% of the energy needed to drive the low altitude electron acceleration processes. This fraction depends on both the level of geomagnetic activity and the assumptions that underlie the integration technique. The similarities between the distribution in time and latitude of the Poynting flux and electron kinetic energy flux extends to low latitudes (≤ 65o ILAT) during major storms. At such times the Poynting flux typically intensify about three orders of magnitude, to intensities of 1 to 10 ergs/cm2s, with such enhancements extending down to latitudes of at least 55o ILAT. The low latitude (≤ 65o ILAT), low altitude electron kinetic energy flux (peak intensities) are typically on the order of 0.1 ergs/cm2s pre storm, and intensifies to the order of 1 to 10s ergs/cm2s during storms. The existence of intense Poynting flux at low latitudes, similar to those at which intense downward electrons are also observed, suggest that Alfven waves are important for, or at least closely related to, low latitude auroral acceleration processes. We also find that though the intense wave Poynting flux tends to occur in conjunction with large scale Poynting flux. And that while the wave Poynting flux is typically an order of magnitude greater in peak intensities, the large scale Poynting flux carries more energy to the ionosphere overall. The arrangement of this thesis is as follows. First, in the introduction, we go over basic space plasma physics with specific focus on energy transfer. We also discuss magnetohydrodynamics (MHD), Alfven waves, and how Alfven waves accelerate auroral electrons. In the second chapter we discuss previous work, both observational and theoretical, on the nature of Alfven wave powered aurora. In the third chapter, we discuss the satellites, the instruments they carry, and other sources of data used in the research presented herein. In chapter four we present the main part of the thesis research, described above in this abstract. In the fifth chapter, we investigate the large scale Poynting flux and its relation to the wave Poynting flux. Finally, in chapter six, the conclusion, we summarize the findings.
机译：在这篇论文中，我们研究了在大地磁风暴过程中，从极光加速区到近地尾的高度，地球夜侧的波和大型珀因廷通量的演化。具体而言，我们正在研究Poynting通量的场定向分量，该分量将能量从尾部带入极光加速区域并传递到电离层，以及下行场定向的电子动能通量。在强风暴坡印定通量期间，在观察到的时间尺度范围内（6-180秒和600 -7200秒）显着增强（一到三个数量级），甚至降至低纬度（≤65o不变纬度）。同时，在相同的纬度范围内，但在低海拔处，向下的电子动能通量至少增加一个数量级。因此，波因廷通量波被证明是风暴期间低纬度地区一种重要的能量传输机制，这提供了有力的证据表明Alfven波可以是低纬度地区极光电子加速的重要机制。该结果很重要，部分原因是低纬度位于映射到内部磁层的磁力线上，并且尚未完全理解与近尾和内部磁层相关的能量传输过程的性质。以前对Alfven波驱动的极光的研究主要集中在极光带和等离子层边界层的较高纬度区域。先前的研究也使用局部航天器结合或长期统计汇编进行。本文介绍的研究是第一个从高空角度逐轨研究大风暴过程中波强廷通量在大风暴过程中（从暴风前，主要阶段和恢复阶段）演化并将其与轨道进行比较的研究。低空电子动能通量。我们发现高空波坡印廷通量和低空电子动能通量强度的经纬度演化很好地吻合。这表明在风暴过程中它们之间存在着一种生成关系。即，要么某些电子被波加速，要么电子和波都由某种第三机制产生。映射波珀因廷通量与极光图像和积分电子动能通量的定量比较表明，珀因廷通量承载着驱动低海拔电子加速过程所需能量的5％到100％以上。这部分取决于地磁活动的水平和整合技术的基础假设。在强风暴期间，珀因廷通量和电子动能通量的时间和纬度分布之间的相似性扩展到低纬度（≤65o ILAT）。在这样的时候，Poynting通量通常会增强大约三个数量级，达到1到10 ergs / cm2s的强度，并且这种增强作用会扩展到至少55o ILAT的纬度。低纬度（≤65o ILAT），低纬度电子动能通量（峰值强度）通常在暴风雨前约为0.1 ergs / cm2s，在暴风雨时增强至1到10s ergs / cm2s。在低纬度上也存在强Poynting通量，这与观察到强烈的向下电子相似，这表明Alfven波对于低纬度极光加速过程很重要，或者至少与之密切相关。我们还发现，尽管强波珀因廷通量倾向于与大规模珀因廷通量一起出现。而且，尽管波音定律通量的峰值强度通常要大一个数量级，但大规模的波音定律通量会将更多的能量带到整个电离层。本文的安排如下。首先，在引言中，我们介绍了基本的空间等离子体物理，重点是能量转移。我们还将讨论磁流体动力学（MHD），Alfven波以及Alfven波如何加速极光电子。在第二章中，我们讨论了先前关于Alfven波供电极光的性质的观测和理论工作。在第三章中，我们讨论了卫星，其携带的仪器以及本文介绍的研究中使用的其他数据源。在第四章中，我们介绍了论文研究的主要部分。在第五章中，我们研究了大规模的波因廷通量及其与波波因廷通量的关系。最后，在第六章的结论中，我们总结了研究结果。

著录项

  • 作者

    Thaller, Scott A.;

  • 作者单位

    University of Minnesota.;

  • 授予单位 University of Minnesota.;
  • 学科 Physics Fluid and Plasma.;Physics General.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 241 p.
  • 总页数 241
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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