NUMERICAL MODELING OF FOOTPOINT-DRIVEN MAGNETO-ACOUSTIC WAVE PROPAGATION IN A LOCALIZED SOLAR FLUX TUBE
NUMERICAL MODELING OF FOOTPOINT-DRIVEN MAGNETO-ACOUSTIC WAVE PROPAGATION IN A LOCALIZED SOLAR FLUX TUBE
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DOI：
10.1088/0004-637x/727/1/17
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发表时间：
2011-01
期刊：
影响因子：
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通讯作者：
V. Fedun;S. Shelyag;R. Erdélyi
中科院分区：
文献类型：
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作者：
V. Fedun;S. Shelyag;R. Erdélyi
在本文中，我们展示并讨论了线性和非线性磁声波在一个开放磁通量管中传播的二维模拟结果，该磁通量管嵌入在从光球层延伸到过渡区并进入低日冕的太阳大气中。我们的目的是对这种磁结构对源自光球层的垂直和水平周期性运动的响应进行建模和分析。为了进行模拟，我们使用了我们的磁流体动力学代码SAC（谢菲尔德先进代码）。在模拟中，将VALIIIC和麦克沃特太阳大气以及日冕密度分布相结合作为背景平衡模型。位于开放磁通量管底部区域的垂直和水平谐波源被纳入计算中，以激发感兴趣区域的振荡。为了进行分析，我们针对计算域的每个高度构建了一系列速度相对于磁场线的垂直和垂直分量的时距图。这些时距图经过时空傅里叶变换，使我们能够为太阳大气中的所有模拟区域构建ω - k色散图。这种方法使得计算在太阳大气模型各个区域传播的波的相速度成为可能。我们展示了线性慢磁声波和快磁声波模式向非线性模式（即冲击波）的转变，并且还表明具有一定频率范围的磁声波有效地通过过渡区泄漏到太阳日冕中。发现对于两种类型的驱动源，波与过渡区相互作用并激发沿过渡区水平传播的表面波。最后，我们估算了太阳日冕中振荡的相速度，并将其与从观测中得出的相速度进行比较。
In this paper, we present and discuss results of two-dimensional simulations of linear and nonlinear magneto-acoustic wave propagation through an open magnetic flux tube embedded in the solar atmosphere expanding from the photosphere through to the transition region and into the low corona. Our aim is to model and analyze the response of such a magnetic structure to vertical and horizontal periodic motions originating in the photosphere. To carry out the simulations, we employed our MHD code SAC (Sheffield Advanced Code). A combination of the VALIIIC and McWhirter solar atmospheres and coronal density profiles were used as the background equilibrium model in the simulations. Vertical and horizontal harmonic sources, located at the footpoint region of the open magnetic flux tube, are incorporated in the calculations, to excite oscillations in the domain of interest. To perform the analysis we have constructed a series of time–distance diagrams of the vertical and perpendicular components of the velocity with respect to the magnetic field lines at each height of the computational domain. These time–distance diagrams are subject to spatio-temporal Fourier transforms allowing us to build ω–k dispersion diagrams for all of the simulated regions in the solar atmosphere. This approach makes it possible to compute the phase speeds of waves propagating throughout the various regions of the solar atmosphere model. We demonstrate the transformation of linear slow and fast magneto-acoustic wave modes into nonlinear ones, i.e., shock waves, and also show that magneto-acoustic waves with a range of frequencies efficiently leak through the transition region into the solar corona. It is found that the waves interact with the transition region and excite horizontally propagating surface waves along the transition region for both types of drivers. Finally, we estimate the phase speed of the oscillations in the solar corona and compare it with the phase speed derived from observations.