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Impulsively generated oscillations in a 3D coronal loop

机译:在3D冠状环中脉冲产生的振荡

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Aims. The effect of changing the attack angle for the interaction of a fast MHD wave with a 3D coronal loop is studied, to investigate to what extent the properties of the excited transverse kink mode oscillations of the loop depend on this angle. Methods. 3D numerical simulations are performed of the interaction of a fast MHD wave, generated by a pressure pulse, with a 3D coronal loop. The loop itself is modelled as a density enhancement (with a finite plasma beta) within a magnetic arcade. The initial pressure pulse has a width comparable to the loop diameter and is situated outside of the loop, at the same height as the loop apex. This height is kept fixed but the (horizontal) angle between the pressure pulse and the loop is varied. Results. We find that the global, transverse kink mode is efficiently excited for a range of attack angles and qualitatively in agreement with theoretical expectations. The period and damping time are found to be independent of the attack angle. For larger values of the attack angle, the global (longitudinal) slow wave is excited, whereas for intermediate values the second harmonic kink mode is also present. Key words: Sun: corona - Sun: oscillations - magnetohydrodynamics (MHD)
机译:目的研究了快速MHD波与3D冠状环相互作用时改变迎角的影响,以研究环的激发横向扭结模式振荡的特性在多大程度上取决于该角度。方法。对压力脉冲产生的快速MHD波与3D冠状环的相互作用进行3D数值模拟。环路本身被建模为电磁场内的密度增强(具有有限的等离子体beta)。初始压力脉冲的宽度与环直径相当,并且位于环外部,与环顶点的高度相同。该高度保持固定,但是压力脉冲和回路之间的(水平)角度是变化的。结果。我们发现,全局,横向扭结模式可在一定的攻角范围内有效激发,并且在质量上与理论预期相符。发现周期和阻尼时间与迎角无关。对于较大的迎角值,将激发全局(纵向)慢波,而对于中等值,还将出现二次谐波扭结模式。关键词:太阳:电晕-太阳:振荡-磁流体动力学(MHD)

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