Origin of two-band chorus in the radiation belt of Earth
Origin of two-band chorus in the radiation belt of Earth
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DOI：
10.1038/s41467-019-12561-3
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发表时间：
2019-10
影响因子：
16.6
通讯作者：
Jinxing Li;J. Bortnik;X. An;Wen Li;V. Angelopoulos;R. Thorne;C. Russell;B. Ni;X. Shen
中科院分区：
文献类型：
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作者：
Jinxing Li;J. Bortnik;X. An;Wen Li;V. Angelopoulos;R. Thorne;C. Russell;B. Ni;X. Shen
自然发生的合唱发射是在地球和其他磁化行星的空间环境中发现的一类电磁波。它们在加速高能电子形成危险辐射带环境方面发挥着重要作用。合唱通常发生在由间隙分隔的两个不同频带中。这种双能带结构的起源仍然是一个 50 年前的问题。在这里，我们使用美国宇航局的范艾伦探测器测量报告，带状合唱波通常伴随着两个独立的各向异性电子分量。通过数值模拟，我们表明最初激发的单带合唱波通过朗道共振立即改变电子分布，并抑制中等能量下的电子各向异性。这自然地将电子各向异性分为低能分量和高能分量，分别激发上带和下带合唱波。这种机制也可能适用于其他磁化行星磁层中合唱波的产生。
Naturally occurring chorus emissions are a class of electromagnetic waves found in the space environments of the Earth and other magnetized planets. They play an essential role in accelerating high-energy electrons forming the hazardous radiation belt environment. Chorus typically occurs in two distinct frequency bands separated by a gap. The origin of this two-band structure remains a 50-year old question. Here we report, using NASA’s Van Allen Probe measurements, that banded chorus waves are commonly accompanied by two separate anisotropic electron components. Using numerical simulations, we show that the initially excited single-band chorus waves alter the electron distribution immediately via Landau resonance, and suppress the electron anisotropy at medium energies. This naturally divides the electron anisotropy into a low and a high energy components which excite the upper-band and lower-band chorus waves, respectively. This mechanism may also apply to the generation of chorus waves in other magnetized planetary magnetospheres.