纳米耀斑加热多股太阳大气环的流体动力学模拟
Hydrodynamic Simulation of a nano-flare heated multi-strand solar atmospheric loop
摘要：
有越来越多的证据表明，目前的仪器（SOHO，TRACE和Hinode）所看到的等离子体环可能由许多次分辨率元素或股组成。因此，我们在这些特征中观察到的整体等离子体演化可能是许多单个股经历零星加热的累积结果。本文提出了一个短（10^9 cm ~ 10 Mm）的“全球循环”，作为125个单独的链，其中每条链是独立的模拟一维流体动力学模拟。跨股的能量释放机制包括局部的、离散的加热事件（纳米耀斑）。通过输入到回路的总能量的频率分布，股线被“耦合”在一起，该频率分布遵循指数为α的幂律分布。每个能量事件发生的位置和寿命是随机的。虽然一个典型的股线可以通过一系列明确定义的加热/冷却循环，当股线相结合，整体准静态排放测量加权热曲线的全球循环再现热顶点/冷基地结构。局部冷等离子体斑点被认为是沿着单独的链，这可能会导致环从日冕发射“消失”，并出现在过渡或色球。随着alpha的增加（从0到2.29再到3.29），最小的加热事件会得到更多的权重。因此，整体环顶点温度增加，而该值周围的温度变化减小。在当前模拟分辨率下，α的任何进一步增加都会使环路顶点温度变化饱和。增加链的数量和环的长度，以及这些结果后，可能的未来观测活动的TRACE和日出的影响的效果进行了讨论。
英文摘要：
There is a growing body of evidence that the plasma loops seen with current instrumentation (SOHO, TRACE and Hinode) may consist of many sub-resolution elements or strands. Thus, the overall plasma evolution we observe in these features could be the cumulative result of numerous individual strands undergoing sporadic heating. This paper presents a short (10^9 cm ~ 10 Mm) ``global loop'' as 125 individual strands where each strand is modelled independently by a one-dimensional hydrodynamic simulation. The energy release mechanism across the strands consists of localised, discrete heating events (nano-flares). The strands are ``coupled'' together through the frequency distribution of the total energy input to the loop which follows a power law distribution with index alpha. The location and lifetime of each energy event occurring is random. Although a typical strand can go through a series of well-defined heating/cooling cycles, when the strands are combined, the overall quasi-static emission measure weighted thermal profile for the global loop reproduces a hot apex/cool base structure. Localised cool plasma blobs are seen to travel along individual strands which could cause the loop to `disappear' from coronal emission and appear in transition or chromospheric ones. As alpha increases (from 0 to 2.29 to 3.29), more weight is given to the smallest heating episodes. Consequently, the overall global loop apex temperature increases while the variation of the temperature around that value decreases. Any further increase in alpha saturates the loop apex temperature variations at the current simulation resolution. The effect of increasing the number of strands and the loop length as well as the implications of these results upon possible future observing campaigns for TRACE and Hinode are discussed.
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