具有横向磁场的磁冕模型中小振幅振荡的衰减
Attenuation of small-amplitude oscillations in a prominence-corona model with a transverse magnetic field
摘要：
小振幅的日珥振荡通常在几个周期后衰减。研究了非绝热磁声波在日冕介质中的板状日珥中的衰减。我们假设一个平衡的配置与横向磁场板轴和调查波阻尼热传导和辐射损失。通过数值求解控制线性快、慢模的微分磁流体动力学方程，得到了系统的复振荡频率和相应的本征函数。我们发现，日冕热传导和辐射损失的日珥等离子体显示为最相关的阻尼机制。这两种机制一起管理的混合模式的衰减，而日珥辐射是负责内部模式的阻尼和日冕传导基本上占主导地位的外部模式的衰减。此外，日珥和日冕之间的热传导引起的能量转移对波的稳定性有明显的影响，日珥等离子体的辐射损失对快模的热稳定性至关重要。我们的结论是，慢模式有效地阻尼，阻尼时间与观察兼容。相反，快模的衰减较少的非绝热效应和他们的阻尼时间是几个数量级以上的观察。的电晕的存在下，导致相对于那些孤立的突出板的阻尼时间的减少，但其效果仍然是不够的，以获得阻尼时间的顺序的周期的情况下，快速模式。
英文摘要：
Small-amplitude prominence oscillations are usually damped after a few periods. We study the attenuation of non-adiabatic magnetoacoustic waves in a slab prominence embedded in the coronal medium. We assume an equilibrium configuration with a transverse magnetic field to the slab axis and investigate wave damping by thermal conduction and radiative losses. The differential MHD equations that govern linear slow and fast modes are numerically solved to obtain the complex oscillatory frequency and the corresponding eigenfunctions. We find that coronal thermal conduction and radiative losses from the prominence plasma reveal as the most relevant damping mechanisms. Both mechanisms govern together the attenuation of hybrid modes, whereas prominence radiation is responsible for the damping of internal modes and coronal conduction essentially dominates the attenuation of external modes. In addition, the energy transfer between the prominence and the corona caused by thermal conduction has a noticeable effect on the wave stability, radiative losses from the prominence plasma being of paramount importance for the thermal stability of fast modes. We conclude that slow modes are efficiently damped, with damping times compatible with observations. On the contrary, fast modes are less attenuated by non-adiabatic effects and their damping times are several orders of magnitude larger than those observed. The presence of the corona causes a decrease of the damping times with respect to those of an isolated prominence slab, but its effect is still insufficient to obtain damping times of the order of the period in the case of fast modes.
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