High-energy particles stream during coronal mass ejections or flares through the plasma of the solar wind. This causes instabilities, which lead to wave growth at specific resonant wave numbers, especially within shock regions. These amplified wave modes influence the turbulent scattering process significantly. In this paper, results of particle transport and scattering in turbulent plasmas with excited wave modes are presented. The method used is a hybrid simulation code, which treats the heliospheric turbulence by an incompressible magnetohydrodynamic approach separately from a kinetic particle description. Furthermore, a semi-analytical model using quasilinear theory (QLT) is compared to the numerical results. This paper aims at a more fundamental understanding and interpretation of the pitch-angle scattering coefficients. Our calculations show a good agreement of particle simulations and the QLT for broad-band turbulent spectra; for higher turbulence levels and particle beam driven plasmas, the QLT approximation gets worse. Especially the resonance gap at $μ=0$ poses a well-known problem for QLT for steep turbulence spectra, whereas test-particle computations show no problems for the particles to scatter across this region. The reason is that the sharp resonant wave--particle interactions in QLT are an oversimplification of the broader resonances in test-particle calculations, which result from nonlinear effects not included in the QLT. We emphasise the importance of these results for both numerical simulations and analytical particle transport approaches, especially the validity of the QLT.
Non-thermal Broadening of IRIS Fe XXI Lines Caused by Turbulent Plasma Flows in the Magnetic Reconnection Region During Solar Eruptions
磁重联是太阳爆发中能量释放的重要机制，其中高温辐射是研究磁重联过程中等离子体性质的主要诊断手段。紫外光谱仪在重联电流片和耀斑环顶区都观测到了高温谱线的非热展宽，但其成因尚不清楚。在这项工作中，我们使用最近开发的三维磁流体动力学（MHD）模拟磁重联在标准的太阳耀斑的几何形状和揭示高度动态的等离子体流的重联区域。利用MHD模型的参数，包括等离子体的密度、温度和速度，计算了界面区成像光谱仪（IRIS）观测到的Fe XXI 1354谱线的合成剖面。我们的模型表明，在CS和耀斑环顶区域的湍流体等离子体流负责的非热加宽的Fe XXI发射线。模拟的非热速度范围从几十公里秒$^{-1}$到超过两百公里秒$^{-1}$，这是与IRIS观测一致。模拟的二维谱线图也揭示了高度动态的下行流结构，其中高的非热速度很大，这是与观测一致的。
Turbulent Magnetogenesis and Large-scale Magnetic Dynamo Amplification in Ion--electron Plasmas
KU Leuven（荷语鲁汶大学）；Royal Belgian Institute for Space Aeronomy（比利时皇家空间空气动力学研究所）；National Research Council (CNR-ISTP)（国家研究委员会）；Università della Calabria（卡拉布里亚大学）；University of Delaware（特拉华大学）
