Collaborative Research: GEM: Propagation and Dissipation of Electromagnetic Ion Cyclotron Waves in the Magnetosphere and Ionosphere

在地球磁层中有许多类型的等离子体波。几十年来，在离子回旋频率附近的pc1 -2频率范围内（0.1-5 Hz）的超低频率电磁离子回旋波是磁层-电离层系统的一个显著特征。这些波在将电离层离子加热为磁层能量、调节磁层压力各向异性、亚暴期间高能重离子填充磁层以及诱导增强质子等方面发挥着重要作用。据了解，地磁场波在内磁层的磁赤道附近以左极化波的形式被激发，并沿磁力线传播到地面。高频地源波在向地面传播过程中往往被滤除，而低频地源波则能有效地到达地面。理解这种现象是很复杂的，因为电磁波可以受到各种物理过程、磁层/电离层传播路径上的等离子体环境以及波的性质的影响。研究小组建议利用模型以及空间和地面观测来更好地理解主位波的传播和耗散。该合作研究项目由来自四个研究所的科学家组成，其中包括两个非r1学院。本项目旨在通过回答以下四个科学问题来研究地磁场波在磁层和电离层中的传播和耗散：主波是如何到达地面的？地磁活动如何影响本源波的传播？地磁场拓扑结构，如压缩和拉伸磁场，如何影响波的传播？在上述参数的背景下，主位波偏振的意义是什么？波偏振与传播有什么关系？该团队将采用最先进的全波模拟代码，peter - m，它使用有限元法（FEM）。采用有限元法的一个优点是在仿真代码中容易采用各种磁场拓扑结构和背景等离子体参数。彼得雷乌斯- m代码将利用实际的地面磁场拓扑结构（偶极子和压缩磁场）和经验密度模型的密度配置。将进行波浪模拟以检验波浪的产生和传播。该小组还将分析最近由多颗卫星对这些波的观测结果，并将其与地面磁力计网络的观测结果进行比较。为了考虑地源波在内磁层中的传播，研究人员将研究空间（GOES卫星）与地面之间的地源波事件、空间分布（L和MLT）、与太阳和地磁活动的关系、GOES卫星与等离子体顶位置之间的距离以及波的极化、频率和法向角等特性。对于外磁层的磁场波，该团队还将研究空间（MMS， THEMIS和Cluster）-使用高纬度地面站进行地面共轭观测。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

There are many types of plasma waves in the Earth's magnetosphere. For decades it has been observed that ultra-low frequency electromagnetic ion cyclotron (EMIC) waves in the Pc 1-2 frequency range (0.1-5 Hz) near the ion cyclotron frequency are a prominent feature of the magnetosphere-ionosphere system. These waves play an important role in heating ionospheric ions to magnetospheric energies, regulating pressure anisotropy in the magnetosphere, populating the magnetosphere with energetic heavy ions during substorms, and inducing enhanced protons. EMIC waves are known to be excited as left-hand polarized waves near the magnetic equator in the inner magnetosphere and reach the ground propagating along the magnetic field line. Higher-frequency EMIC waves are often filtered during wave propagation to the ground, while lower-frequency EMIC waves can effectively reach the ground. Understanding this phenomenon is complicated because EMIC waves can be affected by various physical processes, the plasma environment along the propagation path in the magnetosphere/ionosphere, and wave properties. The team proposed to understand better the propagation and dissipation of EMIC waves using models and both space and ground-based observations. This collaborative research project consists of scientists from four institutes, including two non-R1 colleges. This project aims to investigate the propagation and dissipation of EMIC waves in the magnetosphere and ionosphere by answering these four scientific questions: 1. How do EMIC waves reach the ground?2. How is EMIC wave propagation affected by geomagnetic activity?3. How does geomagnetic field topology, such as compressed and stretched magnetic field, affect wave propagation?4. What is the significance of EMIC wave polarization in the context of the above parameters and how are wave polarizations related with propagation?The team will employ a state-of-art full-wave simulation code, Petra-M, which uses the finite element method (FEM). One advantage of using the FEM is that various magnetic field topologies and background plasma parameters are easily adopted in the simulation code. The Petra-M code will utilize realistic terrestrial magnetic field topologies (dipole and compressed magnetic field) and density configurations from empirical density models. Wave simulations will be performed to examine wave generation and propagation. The team will also analyze recent observations of these waves by multiple satellites and compare them with the ground magnetometer network observations. To consider the EMIC wave propagation in the inner magnetosphere, the proposers will investigate the following characteristics of the EMIC wave events between space (GOES satellite) and ground, spatial distribution (L and MLT), relationship with solar and geomagnetic activity, the distance between GOES satellites and plasmapause locations, and wave properties such as polarization, frequency, and normal angle. For the EMIC waves in the outer magnetosphere, the team will also investigate space (MMS, THEMIS, and Cluster)-ground conjugate observations using high-latitude ground stations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.