Global MHD modeling of resonant ULF waves: Simulations with and without a plasmasphere.
Global MHD modeling of resonant ULF waves: Simulations with and without a plasmasphere.
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DOI：
10.1002/2015ja022048
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发表时间：
2016-01
影响因子：
2.8
通讯作者：
Wiltberger, M.
中科院分区：
文献类型：
--
作者：
Claudepierre, S. G.;Toffoletto, F. R.;Wiltberger, M.
关键词：
利用Lyon-Fedder-Mobarry(LFM)全球磁流体(MHD)模型研究了等离子体层对磁层超低频(ULF)波共振模耦合的影响。我们给出了两个不同版本的模型的结果，都是由相同的太阳风条件驱动的：一个版本包含等离子体层(LFM耦合到莱斯对流模型，其中也包括Gallagher等离子体层模型)，另一个版本不包含等离子体层(独立的LFM)。我们发现，冷密的等离子体层的包含对模拟的超低频波的性质有显著的影响。例如，由于波转折点位置的移动，等离子体层的包含导致了压缩(方位)电场起伏的更深(更接近地面)穿透。因此，压缩电场振荡将其能量共振耦合到局部环向模场线共振的位置也向地球移动。我们还发现，在这两种模拟中，高频压缩(方位)电场振荡比低频振荡穿透得更深。此外，模拟中的纵波模式结构与谐振波导的特征--径向驻波振荡模式一致。将等离子体层结合到LFM全局MHD模型中代表了关于利用这种模拟的ULF波建模的技术水平的进步。我们简要讨论了辐射带建模技术的含义，该技术使用全球MHD模拟的电场和磁场输出来驱动粒子动力学。磁层对太阳风中超低频波动的响应等离子体层的动压包含对模拟的超低频波的性质有很大影响等离子体层的包含导致方位向电场振荡的更深穿透
We investigate the plasmaspheric influence on the resonant mode coupling of magnetospheric ultralow frequency (ULF) waves using the Lyon‐Fedder‐Mobarry (LFM) global magnetohydrodynamic (MHD) model. We present results from two different versions of the model, both driven by the same solar wind conditions: one version that contains a plasmasphere (the LFM coupled to the Rice Convection Model, where the Gallagher plasmasphere model is also included) and another that does not (the stand‐alone LFM). We find that the inclusion of a cold, dense plasmasphere has a significant impact on the nature of the simulated ULF waves. For example, the inclusion of a plasmasphere leads to a deeper (more earthward) penetration of the compressional (azimuthal) electric field fluctuations, due to a shift in the location of the wave turning points. Consequently, the locations where the compressional electric field oscillations resonantly couple their energy into local toroidal mode field line resonances also shift earthward. We also find, in both simulations, that higher‐frequency compressional (azimuthal) electric field oscillations penetrate deeper than lower frequency oscillations. In addition, the compressional wave mode structure in the simulations is consistent with a radial standing wave oscillation pattern, characteristic of a resonant waveguide. The incorporation of a plasmasphere into the LFM global MHD model represents an advance in the state of the art in regard to ULF wave modeling with such simulations. We offer a brief discussion of the implications for radiation belt modeling techniques that use the electric and magnetic field outputs from global MHD simulations to drive particle dynamics. Magnetosphere responds as a resonant waveguide to ULF fluctuations in solar wind dynamic pressure Inclusion of a plasmasphere has a substantial impact on the nature of the simulated ULF waves Inclusion of a plasmasphere leads to a deeper penetration of azimuthal electric field oscillations