Modeling Ultra-Low Frequency (ULF) Waves in the Near-Earth Magnetosphere

超低频（ULF）波在近地磁层的能量传输中起着重要作用。该项目研究将进一步发展用于极低频波研究的磁流体动力学（MHD）模拟，并将将代码应用于涉及磁层中极低频波的几个问题。Pi1波和Pi2波的周期分别为1-40秒和40-150秒，在磁层亚暴发生时经常被观测到。由于这些波可以在世界范围内观测到，它们从震源区到电离层再到地面的传播需要进一步研究。在较长的周期内，Pc3-5波（10-600秒）被用来诊断近地磁层区域的质量分布。在ULF范围的高端，Pc1波（0.2 ~ 5秒）可以与磁层中离子的回旋运动相互作用，引起内磁层的能量和俯仰角散射。这些波可以在所谓的电离层波导中通过电离层传播很远的距离。开发和应用一个可以研究这些相互作用的全球ULF波模型是这个项目的主要目标。这种建模的一个重要方面是将轨道上的航天器观测到的波与地面上的磁力计观测到的波和电离层上的雷达观测到的波联系起来。极低频波的模拟将包括亚暴开始时Pi1和Pi2脉动的动力学，以及它们在高纬度和中纬度与磁尾驱动源相关的时序。改进的MHD模拟代码将使我们能够理解超短波波的瞬态传播以及场线共振的发展，这两者都可以用来诊断磁层的质量密度。将模型扩展到离子回旋效应，将使研究电磁离子回旋波从其源在磁层通过电离层波导的传播成为可能。研究的很大一部分将由研究生进行，他们将接受科学计算艺术方面的训练，以及必要的物理理解，以便不仅解释数值结果，而且解释由卫星、雷达和地面磁力计获得的数据。此外，这项工作还将产生一个用于磁层-电离层耦合的极低频波模型，该模型可应用于磁层物理中的许多问题。

Ultra-low frequency (ULF) waves play a major role in the transport of energy in the near-Earth regions of the magnetosphere. This project research will further develop a magnetohydrodynamic (MHD) simulation for the study of ULF waves and will apply the code to several problems involving ULF waves in the magnetosphere. Pi1 and Pi2 waves, which have periods of 1-40 seconds and 40-150 seconds respectively, are frequently observed at the onset of magnetospheric substorms. Since these waves can be observed world-wide, their propagation from a source region to the ionosphere and to the ground requires further study. At longer periods, Pc3-5 waves (10-600 seconds) have been used as diagnostics of the mass distribution in the near-Earth regions of the magnetosphere. At the high end of the ULF range, Pc1 waves (0.2- 5 seconds) can interact with the cyclotron motion of ions in the magnetosphere and cause energization and pitch angle scattering in the inner magnetosphere. These waves can propagate long distances through the ionosphere in the so-called ionospheric waveguide. Development and application of a global ULF wave model that can investigate these interactions is the primary goal of this project. An important aspect of this modeling is to connect the waves as observed by spacecraft in orbit with waves observed on the ground with magnetometers and in the ionosphere with radar observations. The modeling of ULF waves will include the dynamics of Pi1 and Pi2 pulsations at substorm onset and their timing at both high and mid-latitudes with respect to driving sources in the magnetotail. The improved MHD simulation code will make it possible to understand both the transient propagation of ULF waves as well as the development of field line resonances, both of which can be used to diagnose the mass density of the magnetosphere. The extension of the model to include ion cyclotron effects will make it possible to study the propagation of electromagnetic ion cyclotron (EMIC) waves from their sources in the magnetosphere through the ionospheric waveguide.A significant part of the research will be carried out by graduate students, who will be trained in the art of scientific computation as well as the physics understanding necessary to interpret the results of not only the numerical results but also the data obtained by satellites, radars, and ground magnetometers. In addition, the work will also produce a ULF wave model for magnetosphere-ionosphere coupling that can be applied to many problems in magnetospheric physics.