论文标题
太阳耀斑中的MHD湍流形成：3D模拟和合成观测
MHD turbulence formation in solar flares: 3D simulation and synthetic observations
论文作者
论文摘要
湍流等离子体运动在宇宙中很常见，并在太阳耀斑中调用以驱动有效的加速度，从而导致高能电子。未解决的质量运动经常在极端紫外线（EUV）观测的耀斑中检测到，这些观测通常被视为湍流。但是，这种血浆湍流在耀斑期间如何形成仍然是一个谜。在这里，我们在包括磁重新连接过程的3D磁流体动力学模拟中成功地重现了观察到的湍流。湍流是由于重新连接流出与重新连接位点下方的磁弧之间的复杂的非线性相互作用而形成的，其中剪切流动驱动的kelvin-helmholtz不稳定（KHI）起着产生湍流涡流的关键作用。湍流在高密度耀斑环上产生，然后作为Alfgenic扰动沿磁场传播到沿磁场的色球脚点。在终止冲击周围可以发现高于200 km S^-1的高湍流速度，而低气层在数量密度约为10^11 cm^-3的层上达到10 km S^-1的湍流速度。具有最大非热速度的湍流区域与观察到的高能电子浓缩的区域一致，这表明湍流在加速中的潜在作用。 EUV和拟合的Hinode-eis光谱中的合成视图与观察结果非常吻合。能量分析表明，超过10％的重新连接下流动能可以通过KHI转换为湍流能量。
Turbulent plasma motion is common in the universe, and invoked in solar flares to drive effective acceleration leading to high energy electrons. Unresolved mass motions are frequently detected in flares from extreme ultraviolet (EUV) observations, which are often regarded as turbulence. However, how this plasma turbulence forms during the flare is still largely a mystery. Here we successfully reproduce observed turbulence in our 3D magnetohydrodynamic simulation where the magnetic reconnection process is included. The turbulence forms as a result of an intricate non-linear interaction between the reconnection outflows and the magnetic arcades below the reconnection site, in which the shear-flow driven Kelvin-Helmholtz Instability (KHI) plays a key role for generating turbulent vortices. The turbulence is produced above high density flare loops, and then propagates to chromospheric footpoints along the magnetic field as Alfvenic perturbations. High turbulent velocities above 200 km s^-1 can be found around the termination shock, while the low atmosphere reaches turbulent velocities of 10 km s^-1 at a layer where the number density is about 10^11 cm^-3. The turbulent region with maximum non-thermal velocity coincides with the region where the observed high-energy electrons are concentrated, demonstrating the potential role of turbulence in acceleration. Synthetic views in EUV and fitted Hinode-EIS spectra show excellent agreement with observational results. An energy analysis demonstrates that more than 10% of the reconnection downflow kinetic energy can be converted to turbulent energy via KHI.
