论文标题
紫外线爆发的合理性在低太阳能染色体中
Plausibility of ultraviolet burst generation in the low solar chromosphere
论文作者
论文摘要
紫外线（UV）爆发和Ellerman炸弹（EBS）是在高度分层的低太阳大气中发生的小规模磁重新连接事件。尚不清楚是否必须在大气层更高的大气层下产生紫外线爆发，或者在低染色层中是否可以发生UV爆发和EBS。我们在数值上研究了太阳温度最低区域（TMR）周围的低$β$磁重新连接过程。 MHD代码中包括时间依赖性的氢和氦气电离程度，这导致电子中性碰撞和歧义性扩散引起的更逼真的磁扩散。模拟中包括Carlsson＆Leenaarts 2012的更现实的辐射冷却模型。我们的高分辨率结果表明，如果重新连接磁场高达500美元G，则重新连接区域的等离子体被加热至20,000美元以上，这表明可以在密集的低染色体层中产生紫外线爆发。由于重新连接过程中的局部压缩，在低染色层中产生紫外线爆发的主要机制是加热。调用了血浆介导的湍流重新连接后，重新连接区域中发生的热能被迅速增加。重新连接区域中生成的热能的平均功率密度可以超过$ 1000 $ ERG CM $^{ - 3} $ S $^{ - 1} $，这与紫外线突发的平均功率密度相当。随着重新连接磁场的强度超过$ 900 $ g，合成的SI IV 1394的宽度具有多个峰值的线轮廓可达到$ 100 $ km S $^{ - 1} $，这与观察结果一致。
Ultraviolet (UV) bursts and Ellerman bombs (EBs) are small-scale magnetic reconnection events taking place in the highly stratified, low solar atmosphere. It is still not clear whether UV bursts have to be generated at a higher atmospheric layer than EBs or whether both UV bursts and EBs can occur in the low chromosphere. We numerically studied the low $β$ magnetic reconnection process around the solar temperature minimum region (TMR). The time-dependent ionization degrees of hydrogen and helium are included in the MHD code, which lead to a more realistic magnetic diffusion caused by electron-neutral collision and ambipolar diffusion. A more realistic radiative cooling model from Carlsson & Leenaarts 2012 is included in the simulations. Our results in high resolution indicate that the plasmas in the reconnection region are heated up to more than $20,000$ K if the reconnecting magnetic field is as strong as $500$ G, which suggests that UV bursts can be generated in the dense low chromosphere. The dominant mechanism for producing the UV burst in the low chromosphere is heating, as a result of the local compression in the reconnection process. The thermal energy occurring in the reconnection region rapidly increases after the turbulent reconnection mediated by plasmoids is invoked. The average power density of the generated thermal energy in the reconnection region can reach over $1000$ erg cm$^{-3}$ s$^{-1}$, which is comparable to the average power density accounting for a UV burst. With the strength of the reconnecting magnetic field exceeding $900$ G, the width of the synthesized Si IV 1394 A line profile with multiple peaks can reach up to $100$ km s$^{-1}$, which is consistent with observations.
