Categorization of Electron Isotropy Boundary Patterns: ELFIN and POES Observations

IF 2.6 2区 地球科学 Q2 ASTRONOMY & ASTROPHYSICS
A. V. Artemyev, V. A. Sergeev, V. Angelopoulos, X.-J. Zhang, C. Wilkins
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Abstract

Magnetic field-line curvature scattering (FLCS) of energetic particles in the equatorial magnetotail results in isotropization of pitch-angle distributions, loss-cone filling, and precipitation above a minimum energy at a given latitude. At a fixed energy, the lowest latitude of isotropization is the isotropy boundary (IB) for that energy. Nominally, the IB (latitude) exhibits a characteristic energy dependence due to the monotonic variation of the equatorial magnetic field intensity B e q ${B}_{eq}$ with radial distance. Deviations from this nominal IB dispersion can occur if the radial B e q ${B}_{eq}$ variation (spatial or temporal) is non-mononotic and/or if other precipitation mechanisms prevail. With its sensitive and detailed measurements of electron spectra up to relativistic energies, ELFIN's recent observations reveal a variety of electron IBe patterns near magnetic midnight which are repeatable enough to warrant classification. This study aims to categorize the various IBe patterns observed by ELFIN's high-fidelity but short lived dataset (a few months), compare them with simultaneous nearby POES observations, which are made with a limited energy coverage and resolution but last for decades, and discuss their possible interpretation. The general agreement between ELFIN and POES IB observations indicate a relatively large-scale nature of IBe patterns. Surprisingly, there exists a large number (up to 2/3 of all events) of non-monotonic-or steep/multiple-IB patterns. This suggest an abundance of non-trivial tail current sheet structures or a mixed contribution of two mechanisms in the vicinity of IBe in these cases.

电子各向同性边界图的分类:ELFIN和POES观测
高能粒子在赤道磁尾中的磁场线曲率散射(FLCS)导致了俯仰角分布的各向同性、损失锥填充以及在给定纬度上超过最小能量的降水。在固定能量下,各向同性化的最低纬度是该能量的各向同性边界(IB)。名义上,由于赤道磁场强度B eq ${B}_{eq}$随径向距离的单调变化,IB(纬度)表现出特征的能量依赖。如果径向B eq ${B}_{eq}$变化(空间或时间)是非单调的,和/或如果其他降水机制占上风,则可能发生对名义IB色散的偏离。ELFIN最近的观测显示,它对电子能谱的敏感和详细测量一直到相对论能量,揭示了磁午夜附近的各种电子IBe模式,这些模式可重复到足以保证分类。本研究旨在对ELFIN高保真但寿命较短的数据集(几个月)观测到的各种IBe模式进行分类,将它们与同时进行的附近POES观测进行比较,这些观测具有有限的能量覆盖和分辨率,但持续数十年,并讨论它们可能的解释。ELFIN和POES IB的观测结果基本一致,表明IBe模式具有相对大尺度的性质。令人惊讶的是,存在大量(最多占所有事件的2/3)非单调或陡峭/多重ib模式。这表明在这些情况下,在IBe附近存在丰富的非平凡尾电流片结构或两种机制的混合贡献。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of Geophysical Research: Space Physics
Journal of Geophysical Research: Space Physics Earth and Planetary Sciences-Geophysics
CiteScore
5.30
自引率
35.70%
发文量
570
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