The Role of Magnetic Reconnection-associated Processes in Local Particle Acceleration in the Solar Wind
The Role of Magnetic Reconnection-associated Processes in Local Particle Acceleration in the Solar Wind
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DOI：
10.3847/1538-4357/ab05c6
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发表时间：
2019-03-01
影响因子：
4.9
通讯作者：
Zhao, L. -L.
中科院分区：
文献类型：
--
作者：
Adhikari, L.;Khabarova, O.;Zhao, L. -L.
最近对在1au观测到的异常或非典型高能粒子通量事件（AEPEs）的研究表明，另一种不同于扩散冲击加速的机制可以使太阳风中的局部粒子获得能量。Zank等人提出的机制是基于在超阿尔芬太阳风流中充满大量小尺度磁岛（SMIs）动态收缩或合并并经历多次磁重联的区域中带电粒子的随机赋能。一阶和二阶费米机制是由压缩引起的smi形状变化及其发展动力学引起的。带电粒子也可以通过反重联电场的形成而加速。观测表明，这两个过程在太阳风中经常共存。smi的发生取决于像日球电流片（HCS）这样的强电流片的存在，并且发现相关的AEPEs发生在充满smi的流-流、流-HCS或HCS-激波相互作用形成的磁腔内。以前的案例研究将观察结果与理论预测进行比较，是定性的。在这里，我们提出了基于几个事件的定量理论预测，包括对相应观测结果的详细分析。该研究说明了考虑太阳风中粒子加速局部过程的必要性。
Recent studies of unusual or atypical energetic particle flux events (AEPEs) observed at 1 au show that another mechanism, different from diffusive shock acceleration, can energize particles locally in the solar wind. The mechanism proposed by Zank et al. is based on the stochastic energization of charged particles in regions filled with numerous small-scale magnetic islands (SMIs) dynamically contracting or merging and experiencing multiple magnetic reconnection in the super-Alfvenic solar wind flow. A first- and second-order Fermi mechanism results from compression-induced changes in the shape of SMIs and their developing dynamics. Charged particles can also be accelerated by the formation of antireconnection electric fields. Observations show that both processes often coexist in the solar wind. The occurrence of SMIs depends on the presence of strong current sheets like the heliospheric current sheet (HCS), and related AEPEs are found to occur within magnetic cavities formed by stream-stream, stream-HCS, or HCS-shock interactions that are filled with SMIs. Previous case studies comparing observations with theoretical predictions were qualitative. Here we present quantitative theoretical predictions of AEPEs based on several events, including a detailed analysis of the corresponding observations. The study illustrates the necessity of accounting for local processes of particle acceleration in the solar wind.