Saturation characteristics of electromagnetic ion cyclotron waves
Saturation characteristics of electromagnetic ion cyclotron waves
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DOI：
10.1029/2011ja016638
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发表时间：
2011-09
影响因子：
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通讯作者：
J. Bortnik;N. Omidi;Lunjin Chen;R. Thorne;R. Horne
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文献类型：
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作者：
J. Bortnik;N. Omidi;Lunjin Chen;R. Thorne;R. Horne
[1]电磁离子回旋波是地球动态空间环境的一个组成部分。为了量化它们的影响，有必要知道它们的饱和振幅，但在建模研究中，通常计算线性增长率，并且需要做出各种假设，以便将该增长率与波的最终振幅相关联。在这里，我们使用2.5-D电磁混合PIC代码的EMIC波的饱和特性进行比较，与热等离子体色散求解器的HOTRAY代码计算出相应的线性增长率。我们选择了一组值与卫星观测为我们的名义情况下，并探讨在这个名义情况下，通过改变热质子密度和热各向异性的邻域参数空间。我们发现，饱和振幅单调增加，饱和的时间随着增长率的增加而单调减少，与密度和各向异性的值无关。饱和幅度和饱和时间曲线都可以用简单的双参数模型拟合，误差可以接受。这一结果意味着，在本研究的局限性和警告，饱和振幅和时间饱和可以预测具有良好的准确性的基础上的线性增长率，它可以直接用于与全球环电流模拟的结合，以模拟磁层粒子的综合影响。
[1] Electromagnetic ion cyclotron (EMIC) waves are an integral component of the Earth's dynamic space environment. In order to quantify their effect, it is necessary to know their saturation amplitude, but in modeling studies it is usually the linear growth rate that is calculated and various assumptions need to be made in order to relate this growth rate to the final amplitude of the wave. Here, we perform a comparison of the saturation characteristics of EMIC waves using a 2.5-D electromagnetic hybrid PIC code, with the corresponding linear growth rates calculated with the hot-plasma dispersion solver of the HOTRAY code. We choose a set of values consistent with satellite observations for our nominal case, and explore the parameter space in the neighborhood of this nominal case, by varying the hot proton density and thermal anisotropy. We find that the saturation amplitudes increase monotonically, and the times to saturation decrease monotonically with increasing growth rates, independent of the values of density and anisotropy. Both the saturation amplitude and time to saturation curves can be fit by simple two-parameter models with acceptable errors. This result implies that within the limitations and caveats of the present study, the saturation amplitudes and time to saturation can be predicted with good accuracy based on the linear growth rates alone, which can be used directly in conjunctions with global ring current simulations to model the resultant effects on magnetospheric particles.