The "step feature" of suprathermal ion distributions: a discriminator between acceleration processes?
The "step feature" of suprathermal ion distributions: a discriminator between acceleration processes?
复制标题
超热离子分布的“阶跃特征”：加速过程之间的鉴别器？
DOI：
10.5194/angeo-30-1315-2012
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发表时间：
2012
影响因子：
1.9
通讯作者：
H. Fichtner
中科院分区：
文献类型：
--
作者：
H. Fahr;H. Fichtner
摘要。关于究竟是哪个过程导致了太阳风中超热粒子速度分布的v - 5次幂定律尾部的优先积累的讨论仍在进行中。为了澄清这些尾巴背后的物理原理，允许人们区分各种各样的建议的标准将是有用的。通过这项研究，我们将注意力吸引到速度分布的所谓“阶跃特征”上，并提供了一个标准，允许人们区分那些采用速度扩散的场景，即二阶费米过程，这是目前辩论中的主要候选者。利用自洽得到的速度扩散系数的解析近似，我们求解了过热粒子的输运方程。数值模拟表明，扩散系数的这种形式自然导致了速度分布的阶跃特征。这一发现有利于——至少在阶梯特征出现的区域（即，对于日心距离高达约11天文单位且能量较低的区域）——粒子与等离子体波湍流相互作用的标准速度扩散，而不是由速度波动引起的压缩和稀疏引起的扩散。
Abstract. The discussion of exactly which process is causing the preferred build-up of v−5-power law tails of the velocity distribution of suprathermal particles in the solar wind is still ongoing. Criteria allowing one to discriminate between the various suggestions that have been made would be useful in order to clarify the physics behind these tails. With this study, we draw the attention to the so-called "step feature" of the velocity distributions and offer a criterion that allows one to distinguish between those scenarios that employ velocity diffusion, i.e. second-order Fermi processes, which are prime candidates in the present debate. With an analytical approximation to the self-consistently obtained velocity diffusion coefficient, we solve the transport equation for suprathermal particles. The numerical simulation reveals that this form of the diffusion coefficient naturally leads to the step feature of the velocity distributions. This finding favours – at least in regions of the appearance of the step feature (i.e. for heliocentric distances up to about 11 AU and at lower energies) – the standard velocity diffusion as a consequence of the particle's interactions with the plasma wave turbulence as opposed to that caused by velocity fluctuation-induced compressions and rarefactions.
影响因子：
6.5
作者：
H. Fahr;M. Siewert
通讯作者：
H. Fahr;M. Siewert
太阳风整体速度波动充当共动离子的速度空间扩散
影响因子：
6.5
作者：
Chashei;Siewert
通讯作者：
Siewert