Injection to the pick-up ion regime from high energies and induced ion power-laws
Injection to the pick-up ion regime from high energies and induced ion power-laws
复制标题
从高能量和感应离子幂律注入拾取离子区
DOI：
10.1051/0004-6361/200810755
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发表时间：
2008
影响因子：
6.5
通讯作者：
D. Verscharen
中科院分区：
文献类型：
--
作者：
H. Fahr;I. Chashei;D. Verscharen
虽然吸收离子（pui）是一种众所周知的内日球层现象，但它们的相空间分布在理论上仍然是一个未解决的问题。特别是pui是如何形成超热尾的问题，延伸到远远超过它们的注入能量，现在仍然没有令人满意的答案。尽管费米-2速度扩散理论已经揭示了这样的尾巴是有人口分布的，但它们仍然表明，由此产生的人口密度远低于在速度指数为“- 5”的幂律观测中看到的密度。我们首先在这里研究，观测表明的幂律是否可以是超高温离子和磁流体动力学湍流之间能量交换的准平衡状态的结果。我们证明这样的平衡不能建立，因为它需要太高的PUI压力来强制太阳风的无冲击减速。我们进一步表明，在外日球层中的费米-2型能量扩散效率太低，无法确定那里的分布函数的形状。然而，正如我们所示，如果注入发生在100 keV数量级的更高能量上，则可以建立超过注入阈值的幂律。正如我们在这里所展示的，这种注入与调制的异常宇宙射线（ACR）粒子在其光谱的低端有关，当它们再次开始与太阳风向外对流时。因此，我们将这些颗粒称为acr - pui。在我们对在这种条件下产生的PUI谱的定量计算中，我们实际上再次发现幂律，但是速度-功率指数为“- 4”，光谱强度与距离无关。似乎这些事实在观测上得到了旅行者号在最低能量通道的测量结果的很好支持。
Though pick-up ions (PUIs) are a well-known phenomenon in the inner heliosphere, their phase-space distribution nevertheless is a theoretically unsettled problem. Especially the question of how PUIs form their suprathermal tails, extending to far above their injection energies, still now is unsatisfactorily answered. Though Fermi-2 velocity diffusion theories have revealed that such tails are populated, they nevertheless show that resulting population densities are much less than seen in observations showing power-laws with a velocity index of “−5”. We first investigate here, whether or not observationally suggested power-laws can be the result of a quasi-equilibrium state between suprathermal ions and magnetohydrodynamic turbulences in energy exchange with each other. We demonstrate that such an equilibrium cannot be established, since it would require too high PUI pressures enforcing a shock-free deceleration of the solar wind. We furthermore show that Fermi-2 type energy diffusion in the outer heliosphere is too inefficient to determine the shape of the distribution function there. As we can show, however, power-laws beyond the injection threshold can be established, if the injection takes place at higher energies of the order of 100 keV. As we demonstrate here, such an injection is connected with modulated anomalous cosmic ray (ACR) particles at the lower end of their spectrum when they again start being convected outwards with the solar wind. Therefore, we refer to these particles as ACR-PUIs. In our quantitative calculation of the PUI spectrum resulting under such conditions we in fact find again power-laws, however with a velocity-power index of “−4” and fairly distance-independent spectral intensities. As it seems these facts are observationally well supported by VOYAGER measurements in the lowest energy channels.