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arXiv 1405.0695astro-ph.SR
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太阳大气中磁性元素内的五分钟振荡功率

Five-minute oscillation power within magnetic elements in the solar atmosphere

Rekha Jain, Andrew Gascoyne, Bradley W. Hindman, Benjamin Greer

摘要:

人们早就知道,磁斑和太阳黑子是光球层中声波功率降低的区域。最近的观测结果表明,这种对能量的抑制延伸到了低色球层,并且也存在于远离活动区域的小磁性元素中。在本文中,我们调查所观察到的功率抑制在plage和磁性元素,通过建模作为一个垂直排列的磁纤维的集合,并假设每个纤维内的速度是由入射$p$模式在周围的无场大气抖振的响应。我们限制我们的注意力建模观测太阳盘中心附近,视线速度几乎是垂直的,因此,只有纵向分量的原纤维内的运动作出贡献。因此,我们只考虑轴对称香肠波的激发,而忽略扭结振荡,因为它们的运动主要是水平的。我们通过构造它们的功率比来比较纤维内的垂直运动与入射$p$模式的垂直运动。与观测测量结果一致,我们发现,总功率被抑制在强磁性元件的频率低于声学截止频率。我们还发现,功率赤字的大小增加与上面的光球在测量的高度。此外,我们认为,太阳能盘的面积的功率抑制延伸增加的高度的函数。

英文摘要:

It has long been known that magnetic plage and sunspots are regions in which the power of acoustic waves is reduced within the photospheric layers. Recent observations now suggest that this suppression of power extends into the low chromosphere and is also present in small magnetic elements far from active regions. In this paper we investigate the observed power supression in plage and magnetic elements, by modelling each as a collection of vertically aligned magnetic fibrils and presuming that the velocity within each fibril is the response to buffeting by incident $p$ modes in the surrounding field-free atmosphere. We restrict our attention to modeling observations made near solar disk center, where the line-of-sight velocity is nearly vertical and hence, only the longitudinal component of the motion within the fibril contributes. Therefore, we only consider the excitation of axisymmetric sausage waves and ignore kink oscillations as their motions are primarily horizontal. We compare the vertical motion within the fibril with the vertical motion of the incident $p$ mode by constructing the ratio of their powers. In agreement with observational measurements we find that the total power is suppressed within strong magnetic elements for frequencies below the acoustic cut-off frequency. We also find that the magnitude of the power deficit increases with the height above the photosphere at which the measurement is made. Further, we argue that the area of the solar disk over which the power suppression extends increases as a function of height.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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