Parallel-propagating Fluctuations at Proton-kinetic Scales in the Solar Wind Are Dominated By Kinetic Instabilities
Parallel-propagating Fluctuations at Proton-kinetic Scales in the Solar Wind Are Dominated By Kinetic Instabilities
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DOI：
10.3847/2041-8213/ab4adc
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发表时间：
2019-05
期刊：
影响因子：
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通讯作者：
Lloyd D. Woodham;R. Wicks;D. Verscharen;C. Owen;B. Maruca;B. Alterman
中科院分区：
文献类型：
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作者：
Lloyd D. Woodham;R. Wicks;D. Verscharen;C. Owen;B. Maruca;B. Alterman
我们使用磁螺旋度表征太阳风波动的质子动力学尺度风观测。我们第一次将对螺旋度的贡献从以准平行和倾斜于局部平均磁场的角度传播的波动中分离出来。我们发现准平行涨落的螺旋度与质子温度各向异性不稳定性和α粒子与质子之间存在相对漂移驱动的Alfvén离子回旋和快磁声哨声模式一致。我们还发现斜向涨落的螺旋度对质子温度各向异性的依赖性很小，并且与各向异性湍流级联的涨落一致。我们的研究结果表明，在太阳风质子动力学尺度上的平行传播波动主要是由质子温度各向异性不稳定性，而不是湍流级联。我们还提供了证据表明，在这些尺度上的波动行为是独立的起源和宏观性质的太阳风。
We use magnetic helicity to characterize solar wind fluctuations at proton-kinetic scales from Wind observations. For the first time, we separate the contributions to helicity from fluctuations propagating at angles quasi-parallel and oblique to the local mean magnetic field, . We find that the helicity of quasi-parallel fluctuations is consistent with Alfvén-ion cyclotron and fast magnetosonic-whistler modes driven by proton temperature anisotropy instabilities and the presence of a relative drift between α-particles and protons. We also find that the helicity of oblique fluctuations has little dependence on proton temperature anisotropy and is consistent with fluctuations from the anisotropic turbulent cascade. Our results show that parallel-propagating fluctuations at proton-kinetic scales in the solar wind are dominated by proton temperature anisotropy instabilities and not the turbulent cascade. We also provide evidence that the behavior of fluctuations at these scales is independent of the origin and macroscopic properties of the solar wind.