Relativistic electrons in the outer radiation belt: Differentiating between acceleration mechanisms
Relativistic electrons in the outer radiation belt: Differentiating between acceleration mechanisms
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DOI：
10.1029/2003ja010153
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发表时间：
2004-03-18
影响因子：
2.8
通讯作者：
Kivelson, MG
中科院分区：
文献类型：
--
作者：
Green, JC;Kivelson, MG
[1]许多理论模型已经被开发出来，以解释形成地球辐射带的电子快速加速到相对论能量。然而，经过几十年的研究，这些模型都没有通过与观测结果的比较得到明确的证实。提出的模型可以分为两种类型：内部和外部源加速机制。内部源加速机制加速已经存在于内磁层中的电子（L < 6.6），而外部源加速机制将电子的源群从外磁层运输和加速到内磁层。在原则上，这两种类型的加速机制可以区分，因为它们意味着不同的径向梯度的电子相空间密度表示为三个绝热不变量的函数将开发。模型预测可以通过将测量的电子通量（作为俯仰角、能量和位置的函数给出）转换为作为三个不变量μ、K和Phi的函数的相空间密度来测试。这种变换需要采用磁场模型。相空间密度估计，在过去，产生矛盾的结果，因为有限的测量和场模型误差。在这项研究中，我们大大减少了以前的工作的不确定性和帐户的矛盾。我们使用的数据主要来自极地航天器上的极地高灵敏度望远镜高能探测器和Tsyganenko和Stern [1996]场模型，以获得相空间密度。我们将展示不完美的磁场模型如何产生相空间密度误差，并探讨这些误差如何修改解释。在分析的基础上，我们得出结论，数据最好的解释模型，需要加速的内部电子源附近的L* 类似于5。我们还建议，从一个相空间密度峰值L* 附近的向外径向扩散类似5可以解释观测到的对应关系通量增强在地球静止轨道和超低频波功率的增加。
[1] Many theoretical models have been developed to explain the rapid acceleration to relativistic energies of electrons that form the Earth's radiation belts. However, after decades of research, none of these models has been unambiguously confirmed by comparison to observations. Proposed models can be separated into two types: internal and external source acceleration mechanisms. Internal source acceleration mechanisms accelerate electrons already present in the inner magnetosphere (L < 6.6), while external source acceleration mechanisms transport and accelerate a source population of electrons from the outer to the inner magnetosphere. In principle, the two types of acceleration mechanisms can be differentiated because they imply that different radial gradients of electron phase space density expressed as a function of the three adiabatic invariants will develop. Model predictions can be tested by transforming measured electron flux (given as a function of pitch angle, energy, and position) to phase space density as a function of the three invariants, mu, K, and Phi. The transformation requires adoption of a magnetic field model. Phase space density estimates have, in the past, produced contradictory results because of limited measurements and field model errors. In this study we greatly reduce the uncertainties of previous work and account for the contradictions. We use data principally from the Polar High Sensitivity Telescope energetic detector on the Polar spacecraft and the Tsyganenko and Stern [1996] field model to obtain phase space density. We show how imperfect magnetic field models produce phase space density errors and explore how those errors modify interpretations. On the basis of the analysis we conclude that the data are best explained by models that require acceleration of an internal source of electrons near L* similar to 5. We also suggest that outward radial diffusion from a phase space density peak near L* similar to 5 can explain the observed correspondence between flux enhancements at geostationary orbit and increases in ULF wave power.