Structure of an energetic narrow discrete arc
Structure of an energetic narrow discrete arc
复制标题
能量窄离散弧的结构
DOI：
10.1029/ja095ia05p06533
复制
发表时间：
1990
影响因子：
--
通讯作者：
M. Boehm
中科院分区：
文献类型：
--
作者：
J. Mcfadden;C. Carlson;M. Boehm
粒子分布、波、直流电场和磁场由两枚探空火箭在950公里和430公里的高度通过高能（>5 keV）窄（约10公里）稳定的离散弧测量。虽然有效载荷的磁足迹仅相隔50公里，但观察到电弧结构的差异，包括空间宽度，峰值能量和特征光谱。充满活力的电子沉淀包括缓慢变化的各向同性通量，形成了一个倒V的能量-时间签名和快速变化的场对齐的通量或低于各向同性的光谱峰值。各向同性的沉淀弧内有一个通量的不连续性，表明电弧是存在于两个不同的磁层等离子体之间的边界。在整个电弧中测量了场对准电子的分散和非分散爆发，出现在宽的能量范围内或作为单能束。分散爆发给出了可变的源距离<8000公里。一些最强烈的爆发的平台表明波稳定了这些电子。在低海拔弧交叉，场对准的组件形成了一个单独的倒V型能量-时间签名，其峰值能量是各向同性峰值能量的一半。这种结构表明，两个独立的电位降可能已经形成沿着同一个通量管，冷等离子体存在于它们之间。电子分布的高时间分辨率测量，以及电流系统，等离子体流和等离子体波的测量，提供了一个详细的窄弧的图片。这套完整的测量结果说明了狭窄的离散弧中存在的复杂结构，并证明了多个航天器进行高分辨率测量的优势。
Particle distributions, waves, dc electric fields and magnetic fields were measured by two sounding rockets at altitudes of 950 and 430 km through an energetic (>5 keV) narrow (∼10 km) stable discrete arc. Although the payloads' magnetic footprints were separated by only 50 km, differences in the arc's structure were observed including the spatial width, peak energy, and characteristic spectra. The energetic electron precipitation included both slowly varying isotropic fluxes that formed an inverted-V energy-time signature and rapidly varying field-aligned fluxes at or below the isotropic spectral peak. The isotropic precipitation had a flux discontinuity inside the arc indicating the arc was present on a boundary between two different magnetospheric plasmas. Dispersive and nondispersive bursts of field-aligned electrons were measured throughout the arc, appearing over broad energy ranges or as monoenergetic beams. Dispersive bursts gave variable source distances <8000 km. Plateauing of some of the most intense bursts suggests that waves stabilized these electrons. During the lower altitude arc crossing, the field-aligned component formed a separate inverted-V energy-time signature whose peak energy was half the isotropic peak energy. This structure suggests that two separate potential drops may have formed along the same flux tube with cold plasma present between them. High time resolution measurements of electron distributions, together with measurements of the current system, plasma flows, and plasma waves, provide a detailed picture of the narrow arc. This complete set of measurements illustrates the complex structure present in narrow discrete arcs and demonstrates the advantages of high resolution measurements by multiple spacecraft.