The radiative response of solar loop plasma subject to transient heating
The radiative response of solar loop plasma subject to transient heating
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瞬态加热下太阳环路等离子体的辐射响应
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
H. Mason
中科院分区：
文献类型：
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作者：
S. Bradshaw;H. Mason
在Bradshaw & Mason（2003）中，我们对冷却太阳环进行了流体动力学模拟，并研究了C VII离子总数对等离子体中变化条件的非平衡响应。我们还比较了等离子体总发射率的平衡和非平衡计算。在本文中，我们提出了两个模拟的太阳能环路的瞬态加热过程中提供能量的纳米耀斑规模在其顶点。一个模拟处理的离子种群和能量辐射的环路等离子体完全，好像系统处于平衡状态，另一个模拟进行一个完整的非平衡处理耦合的时间依赖的离子种群的流体动力学方程，通过辐射能量损失。我们的辐射模型考虑了太阳大气中15种最丰富的元素，包括C，O，Ne，Mg，Si和Fe。在平衡态和非平衡态模拟中，我们发现某些过渡区离子的数量与相应的等离子体发射率曲线之间存在着明显的差异。虽然顶点加热事件是相对较弱的微耀斑和耀斑尺度上释放的能量相比，然而，大量的能量到达环路足点区域加热等离子体，我们发现一个非平衡尖峰发射率。然而，更令人惊讶的是，我们发现相当大的diepheres之间的一些日冕离子在平衡和非平衡模拟，等离子体发射率曲线的重要后果。特别是，我们发现，假设平衡条件下计算的总等离子体发射率是一个因素的5低于非平衡发射率，这是由于几乎完全的响应的冠状铁离子。最后，我们提出了可能的观测签名的非平衡电离和方法，其中一个可能识别it. This是重要的，因为一个无效的假设平衡离子种群可能会导致一个不正确的结论，在宽带和窄带/发射线为基础的分析等离子体的属性。
In Bradshaw & Mason (2003) we carried out a hydrodynamic simulation of a cooling solar loop and investigated the nonequilibrium response of the population of C VII ions to the changing conditions in the plasma. We also compared equilibrium and nonequilibrium calculations of the total plasma emissivity. In this paper we present two simulations of a solar loop subject to a transient heating process delivering energy on the nanoflare scale at its apex. One simulation treats the ion populations and the energy radiated from the loop plasma entirely as though the system were in equilibrium and the other simulation performs a full nonequilibrium treatment by coupling the time-dependent ion populations to the hydrodynamic equations through the radiative energy loss. Our radiative model accounts for the 15 most abundant elements of the solar atmosphere including C, O, Ne, Mg, Si and Fe. We find some pronounced dierences between the populations of certain transition region ions and the corresponding plasma emissivity curves in the equilibrium and nonequilibrium simulations. Though the apex heating event is relatively weak in comparison to energy released on the microflare and flare scales, nonetheless a significant amount of energy reaches the loop footpoint region to heat the plasma there and we find a nonequilibrium spike in emissivity. However, more surprisingly we find considerable dierences between some of the coronal ions in the equilibrium and nonequilibrium simulations, with important consequences for the plasma emissivity curves. In particular, we find that the total plasma emissivity calculated assuming equilibrium conditions is up to a factor of 5 lower than the nonequilibrium emissivity and this is due almost entirely to the response of the coronal Fe ions. Finally, we suggest possible observational signatures of nonequilibrium ionisation and ways in which one might identify it. This is important because an invalid assumption of equilibrium ion populations may well lead one to incorrect conclusions about the properties of the plasma in both a broad-band and narrow-band/emission line based analysis.