The “zebra stripes”: An effect of F region zonal plasma drifts on the longitudinal distribution of radiation belt particles
The “zebra stripes”: An effect of F region zonal plasma drifts on the longitudinal distribution of radiation belt particles
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“斑马条纹”：F区带状等离子体漂移对辐射带粒子纵向分布的影响
DOI：
10.1002/2015ja021925
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
J. Roederer
中科院分区：
文献类型：
--
作者：
S. Lejosne;J. Roederer
我们考察了一种特征效应，即在L ~ 3下方的内带中捕获的高能电子和离子的谱图中普遍出现的称为斑马条纹的结构峰和谷。我们提出了对这一现象的纯粹运动学解释，认为这是电离层F区带状等离子体漂移引起的粒子漂移速度调制的纯粹运动学结果。换句话说，我们修正了传统的假设，即与电离层等离子体相关的电场驱动囚禁粒子分布与地球发生刚性公转。基于一个简单的一阶模型，建立了一个方程，定量地确定了斑马条的外观作为磁时间的函数。我们的数值预测与Van Allen探测器上的辐射带风暴探测器离子组成实验探测器的测量结果是一致的，即：(1)在白天光谱中确定的任何峰值的中心能量是夜晚光谱谷的中心能量；(2)当比较捕获电子的光谱和相同位置的捕获离子的光谱时，也存在近似的峰到谷反转；以及(3)被捕获粒子群光谱中两个连续峰(或条带数)之间的实际能量间隔是粒子在安静条件下漂移所花费时间的指标。
We examine a characteristic effect, namely, the ubiquitous appearance of structured peaks and valleys called zebra stripes in the spectrograms of energetic electrons and ions trapped in the inner belt below L ~ 3. We propose an explanation of this phenomenon as a purely kinematic consequence of particle drift velocity modulation caused by F region zonal plasma drifts in the ionosphere. In other words, we amend the traditional assumption that the electric field associated with ionospheric plasma drives trapped particle distributions into rigid corotation with the Earth. An equation based on a simple first‐order model is set up to determine quantitatively the appearance of zebra stripes as a function of magnetic time. Our numerical predictions are in agreement with measurements by the Radiation Belt Storm Probes Ion Composition Experiment detector onboard Van Allen Probes, namely: (1) the central energy of any peak identified in the spectrum on the dayside is the central energy of a spectral valley on the night side, and vice versa; (2) there is also an approximate peak‐to‐valley inversion when comparing the spectrum of trapped electrons with that of trapped ions in the same place; and (3) the actual energy separation between two consecutive peaks (or number of stripes) in the spectrogram of a trapped population is an indicator of the time spent by the particles drifting under quiet conditions.