High-frequency Spicule Oscillations Generated via Mode Conversion
High-frequency Spicule Oscillations Generated via Mode Conversion
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DOI：
10.3847/1538-4357/aaa54f
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发表时间：
2018-01
期刊：
影响因子：
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通讯作者：
M. Shoda;T. Yokoyama
中科院分区：
文献类型：
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作者：
M. Shoda;T. Yokoyama
针状振荡涉及高频成分，典型周期约为 40-50 秒。光球振荡的典型时间尺度是几分钟，因此，这种高频分量的起源并非微不足道。在这项研究中，进行一维数值模拟以证明观察到的针状振荡源自色球均分层周围发生的纵向到横向模式转换。除了额外加热以维持日冕温度之外，计算以自洽的方式进行。分析表明，具有以下特点：（1）模式转换有效激发高频横波； (2)高频波的典型周期对应于模式转换区域的声音穿越时间； (3)模拟的高频分量均方根速度与观测值一致。这些结果表明，针状振荡的观察提供了色球层模式转换的直接证据。
Spicule oscillations involve high-frequency components with a typical period approximately corresponding to 40–50 s. The typical timescale of the photospheric oscillation is a few minutes, and thus, the origin of this high-frequency component is not trivial. In this study, a one-dimensional numerical simulation is performed to demonstrate that the observed spicule oscillations originate from longitudinal-to-transverse mode conversion that occurs around the equipartition layer in the chromosphere. Calculations are conducted in a self-consistent manner with the exception of additional heating to maintain coronal temperature. The analyses indicate the following features: (1) mode conversion efficiently excites high-frequency transverse waves; (2) the typical period of the high-frequency waves corresponds to the sound-crossing time of the mode conversion region; and (3) simulated root-mean-square velocity of the high-frequency component is consistent with the observed value. These results indicate that the observation of spicule oscillation provides direct evidence of mode conversion in the chromosphere.