Observations of particles precipitating into detached arcs and patches equatorward of the auroral oval
Observations of particles precipitating into detached arcs and patches equatorward of the auroral oval
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对极光卵圆赤道方向沉淀成分离弧和斑块的粒子的观察
DOI：
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发表时间：
1979
期刊：
影响因子：
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通讯作者：
J. Murphree
中科院分区：
文献类型：
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作者：
D. Wallis;J. Burrows;M. C. Moshupi;C. Anger;J. Murphree
当航天器与映射到极光椭圆形赤道方向的光发射区域的场线相交时，Isis 2 上的高能粒子探测器进行的粒子观测有时会受到检查。这些发射以弧和斑块的形式出现，被称为分离弧[Anger et al., 1978]和斑块[Moshupi et al., 1977]。这些形式存在于场力线的底部，该场力线具有被捕获的电子群 1 ≤ Ee ≤ 10 keV 以及通常的高能辐射带粒子。在光学形式上方观察到这些被捕获的粒子在高达 210 keV 的所有能量下的沉淀。在两种情况下，详细的比较证实沉淀电子携带足够的能量通量来解释观察到的发射强度。研究发现，每一个分离的弧和除了一个之外的所有斑块都出现在一端“阳光照射”的场线上，并且可能携带光电子。尽管光电子在引起降水中的作用尚不清楚，但一端黑暗、另一端阳光照射的场线的地理和本地时间分布与观察到的分离弧的分布相一致。粒子观测要求降水是由俯仰角散射引起的，散射角略大于损失锥。提出了一个经验模型，其中在地球周围漂移的被捕获的残余等离子体片群在进入等离子体层顶之外固定在 L-MLT 中的散射区域时会沉淀。降水的空间限制及其与观察到的分离等离子体区域的相似性表明，散射区域具有增强的冷等离子体密度。电子回旋共振被检查为俯仰角散射的原因，并发现与观察结果一致。
Particle observations made by the energetic particle detector on board Isis 2 are examined at times when the spacecraft intersects field lines mapping into regions of optical emission equatorward of the auroral oval. These emissions appear as arcs and patches and have been called detached arcs [Anger et al., 1978] and patches [Moshupi et al., 1977]. The forms are found at the feet of field lines having a trapped population of electrons 1 ≤Ee ≤10 keV as well as the usual higher-energy radiation belt particles. Precipitation of these trapped particles at all energies up to 210 keV is observed above the optical forms. In two cases, detailed comparison confirmed that the precipitating electrons carries sufficient energy flux to account for the observed emission intensities. It is found that each of the detached arcs and all but one of the patches occur on field lines which have one end ‘sunlit’ and presumably carry photoelectrons. The geographic and local time distribution of field lines which are dark at one end and sunlit at the other is compatible with the observed distribution of detached arcs, although the role of photoelectrons in causing precipitation is not clear. The particle observations require that precipitation be caused by pitch angle scattering with scattering angle slightly larger than the loss cone. An empirical model is suggested in which a trapped, residual plasma sheet population drifting about the earth is precipitated when it enters scattering regions fixed in L-MLT outside the plasmapause. The spatial confinement of the precipitation and its similarity to observed detached plasma regions suggest that the scattering regions have enhanced cold plasma densities. Electron cyclotron resonance is examined as the cause of the pitch angle scattering and found to be consistent with the observations.