Impact of compressibility and a guide field on Fermi acceleration during magnetic island coalescence
Impact of compressibility and a guide field on Fermi acceleration during magnetic island coalescence
复制标题
磁岛聚结过程中压缩性和引导场对费米加速度的影响
DOI：
10.1063/1.4985302
复制
发表时间：
2017
影响因子：
2.2
通讯作者：
B. Wetherton
中科院分区：
文献类型：
--
作者：
P. Montag;J. Egedal;E. Lichko;B. Wetherton
先前的工作表明，费米加速可以是磁岛聚结过程中的一种有效加热机制，其中随着磁场线收缩，电子可能会经历反复反射。这种能量有可能解释从太阳耀斑观测中推断出的粒子能量的幂律分布。在这里，我们开发了一个用于分析费米加速度的通用框架，该框架可以结合沿场线的可压缩性和不均匀性的影响，而这些影响在以前的问题处理中通常被忽略。将此框架应用于均匀通量管的简化情况使我们能够找到分布函数的幂律缩放和幂律行为发展的速率。我们发现有序统一的引导磁场有效地抑制了幂律分布的发展。
Previous work has shown that Fermi acceleration can be an effective heating mechanism during magnetic island coalescence, where electrons may undergo repeated reflections as the magnetic field lines contract. This energization has the potential to account for the power-law distributions of particle energy inferred from observations of solar flares. Here, we develop a generalized framework for the analysis of Fermi acceleration that can incorporate the effects of compressibility and non-uniformity along field lines, which have commonly been neglected in previous treatments of the problem. Applying this framework to the simplified case of the uniform flux tube allows us to find both the power-law scaling of the distribution function and the rate at which the power-law behavior develops. We find that a guide magnetic field of order unity effectively suppresses the development of power-law distributions.