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Lower‐Band “Monochromatic” Chorus Riser Subelement/Wave Packet Observations
Journal of Geophysical Research: Space Physics ( IF 2.8 ) Pub Date : 2020-09-22 , DOI: 10.1029/2020ja028090
Bruce T. Tsurutani 1 , Rui Chen 2, 3 , Xinliang Gao 2, 3 , Quanming Lu 2, 3 , Jolene S. Pickett 4 , Gurbax S. Lakhina 5 , Abhijit Sen 6 , Rajkumar Hajra 7 , Sang A Park 8 , Barbara J. Falkowski 9
Affiliation  

Three lower‐band (f < 0.5 fce) chorus riser elements detected in the dayside generation region were studied in detail using the Van Allen Probe data. Two subelements/wave packets within each riser were examined for their wave “frequency” constancy within seven consecutive wave cycles. The seven wave cycles contained the maximum amplitudes of the subelements/packets. Maximum variance B1 zero crossings were used for the identification of wave cycle start and stop times. It is found that the frequency is constant to within ~3% (one standard deviation), with no evidence of upward frequency sweeping over the seven cycles. Continuous wavelet power spectra for the duration of the seven cycles confirm this conclusion. The implication is that a chorus riser element is composed of coherent approximately “monochromatic” steps instead of a gradual sweep in frequency over the whole element. There was no upward frequency stepping where the wave amplitude was the largest, contrary to the sideband theory prediction. It is shown that © 2020 California Institute of Technology a chorus riser involves instability of cyclotron resonant energetic electrons from ~6 to ~40 keV at L = 5.8, that is, essentially the whole substorm electron energy spectrum. The above findings may have important consequences for possible wave generation mechanisms. Some new ideas for mechanisms are suggested in conclusion.

中文翻译:

较低频段的“单色”合唱立管子元素/波包观测

三个低频段(f 使用Van Allen Probe数据详细研究了在白天生成区域中检测到的<0.5 fce)合唱立管元素。检查了每个立管内的两个子元素/波包在七个连续波周期内的波“频率”恒定性。七个波周期包含子元素/数据包的最大振幅。最大方差B1过零用于确定波浪周期的开始和停止时间。发现频率恒定在〜3%以内(一个标准偏差),没有证据表明在七个周期内都有向上的频率扫描。在七个周期的持续时间内连续的小波功率谱证实了这一结论。这意味着合唱立管元件由相干的近似“单色”阶梯组成,而不是整个元件上的频率逐渐扫描。与边带理论预测相反,在波幅最大的位置没有向上的频率步进。结果表明,©2020年,加州理工学院的一个合唱上升管涉及回旋加速器共振高能电子,在约6 keV至约40 keV时不稳定。L  = 5.8,即基本上是整个亚暴电子能谱。以上发现可能会对可能的波浪产生机制产生重要影响。结论中提出了一些新的机制构想。
更新日期:2020-10-15
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