标题： 用光学厚辐射损失建模太阳低高度冷环 显示英文标题

标题： Modelling solar low-lying cool loops with optically thick radiative losses

摘要： 我们研究了由于小而冷的磁环（高度$\lesssim8$~Mm，$T\lesssim10^5$~K）向色球层的增加导致的DEM（差分发射量）的增加。 在之前的一篇论文中，我们通过流体动力学模拟分析了这些环的存在和稳定性条件，重点研究了它们对所使用光学薄辐射损失函数细节的依赖性。 在本文中，我们将这些流体动力学模拟扩展到验证当使用光学厚辐射损失函数时，这类环是否存在且稳定。 我们研究了两种情况：恒定背景加热和与密度相关的加热。 这些环对过渡区极紫外输出的贡献也进行了计算并展示了。 我们发现，通过使用光学厚辐射损失函数和与密度相关的背景加热，可以获得稳定、准静态的冷环。 然而，这些环的DEM无法再现温度在$4.6<\log T<4.8$之间的观测DEM。 我们还展示了考虑恒定加热率获得的动力学环的瞬态阶段，并发现其平均DEM，作为一组演化的动态环来解释，可以很好地再现观测到的DEM。 显示英文摘要

摘要： We investigate the increase of the DEM (differential emission measure) towards the chromosphere due to small and cool magnetic loops (height $\lesssim8$~Mm, $T\lesssim10^5$~K). In a previous paper we analysed the conditions of existence and stability of these loops through hydrodynamic simulations, focusing on their dependence on the details of the optically thin radiative loss function used. In this paper, we extend those hydrodynamic simulations to verify if this class of loops exists and it is stable when using an optically thick radiative loss function. We study two cases: constant background heating and a heating depending on the density. The contribution to the transition region EUV output of these loops is also calculated and presented. We find that stable, quasi-static cool loops can be obtained by using an optically thick radiative loss function and a background heating depending on the density. The DEMs of these loops, however, fail to reproduce the observed DEM for temperatures between $4.6<\log T<4.8$. We also show the transient phase of a dynamic loop obtained by considering constant heating rate and find that its average DEM, interpreted as a set of evolving dynamic loops, reproduces quite well the observed DEM.