Early Time Evolution of Turbulence in the Space Environment by Neutral Beam Injection
Early Time Evolution of Turbulence in the Space Environment by Neutral Beam Injection
复制标题
中性束注入空间环境中湍流的早期演化
DOI：
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
C. Siefring
中科院分区：
文献类型：
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作者：
A. Fletcher;C. Crabtree;J. Huba;G. Ganguli;C. Siefring
火箭释放湍流的空间测量任务将通过一系列等离子体物理过程演示空间环境中湍流的产生和演变。探空火箭将以高速穿越磁场的方式将中性钡原子注入电离层上层。钡原子光离，磁场限制它们，导致离子环分布在速度空间，是不稳定的静电低杂化波。低杂波的非线性诱导散射产生电磁、磁声子和哨声波，这些波迅速逃离源区并传播到辐射带中。在本文中，我们提出了该级联的早期部分的模型和模拟，直到产生较低的混合波。我们用分析和计算的方法研究了中性原子的注入、膨胀和电离。在实际情况下，发现速度分布函数在垂直于磁场的平面上不是一个完美的环，而是一个非匀速分布函数。利用这些结果，我们研究了钡云的一个代表性区域，并对较低混合波的激发进行了粒子-细胞模拟。特别令人感兴趣的是从钡离子的动能中提取的能量，因为这将最终影响辐射带中电磁波的振幅。我们发现，当速度分布函数偏离理想的环形分布时，从快速钡离子中提取的能量增加。
The Space Measurement of A Rocket‐released Turbulence mission will demonstrate the production and evolution of turbulence in the space environment via a cascade of plasma physics processes. A sounding rocket will inject neutral barium atoms into the upper ionosphere at high speed across the magnetic field. The barium atoms photoionize, and the magnetic field confines them, leading to an ion ring distribution in velocity space that is unstable to electrostatic lower hybrid waves. Nonlinear induced scattering of lower hybrid waves produces electromagnetic magnetosonic and whistler waves that rapidly escape the source region and propagate into the radiation belts. In this paper, we present models and simulations of early time parts of this cascade until the lower hybrid waves are generated. We study the neutral atom injection, expansion, and ionization analytically and computationally. In a realistic scenario, the velocity distribution function is found to be nongyrotropic instead of a perfect ring in the plane perpendicular to the magnetic field. Using these results, we examine a representative region of the barium cloud and perform particle‐in‐cell simulations of the excitation of the lower hybrid waves. Of particular interest is the energy extracted from the kinetic energy of the barium ions, as this will ultimately affect the amplitude of the electromagnetic waves in the radiation belts. We find that for velocity distribution functions that deviate from an ideal ring distribution, the energy extracted from the fast barium ions increases.