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

超低频波在磁层近地区域的能量传输中发挥着重要作用。这一项目研究将进一步开发磁流体动力学(MHD)模拟来研究超低频波，并将把该程序应用于涉及磁层中超低频波的几个问题。Pi1波和Pi2波的周期分别为1-40秒和40-150秒，在磁层亚暴开始时经常被观测到。由于可以在世界范围内观测到这些波，因此需要进一步研究它们从源区向电离层和地面的传播。在更长的周期内，PC3-5波(10-600秒)被用来诊断磁层近地区域的质量分布。在超低频范围的高端，Pc1波(0.2-5秒)可以与磁层中离子的回旋运动相互作用，并在内部磁层引起能量和俯仰角散射。这些波可以在所谓的电离层波导中通过电离层传播很长距离。本项目的主要目标是开发和应用一个能够研究这些相互作用的全球ULF波模式。这种模拟的一个重要方面是将航天器在轨道上观测到的波与地面磁力计观测到的波以及电离层中的波与雷达观测联系起来。ULF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相对于磁尾驱动源的时间安排。改进后的MHD模拟程序将使理解超低频波的瞬时传播和场线共振的发展成为可能，这两者都可以用来诊断磁层的质量密度。将模型扩展到包括离子回旋效应，将使研究电磁离子回旋(EMIC)波在磁层中通过电离层波导的传播成为可能。这项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和物理理解方面的培训，不仅解释数值结果，还解释卫星、雷达和地面磁强计获得的数据。此外，这项工作还将产生磁层-电离层耦合的超低频波模型，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.