THE ORIGIN OF TYPE I SPICULE OSCILLATIONS
THE ORIGIN OF TYPE I SPICULE OSCILLATIONS
复制标题
DOI：
10.1088/2041-8205/744/1/l5
复制
发表时间：
2011-11
期刊：
影响因子：
--
通讯作者：
D. Jess;D. Pascoe;D. Christian;M. Mathioudakis;P. Keys;F. Keenan
中科院分区：
文献类型：
--
作者：
D. Jess;D. Pascoe;D. Christian;M. Mathioudakis;P. Keys;F. Keenan
我们利用邓恩太阳望远镜的太阳大气快速振荡仪器获得的高时空分辨率图像，揭示了I型针状体中横波的产生是如何由光球中发生的纵向振荡直接导致的。在这里，我们展示了周期性在130-440秒范围内的压力振荡如何在小尺度光球磁亮点中表现出来，并在太阳外层大气中产生横向速度接近当地声速的扭结波。通过将我们的观测结果与先进的二维磁流体动力学模拟进行比较，我们提供了证据，证明在太阳表面产生的磁声振荡如何沿着I型针状结构向上漏斗，然后在两倍于初始驱动频率的情况下经历纵向到横向模式转换为波。由此产生的扭结模式在色球等离子体中可见，其周期为65-220秒，振幅通常超过400公里。在模拟和观测的时间序列中都可以看到，由于光球驱动，也会产生香肠型振荡。我们得出结论，模式转换和周期修正是围绕光球驱动器两侧的90°相移的直接结果。这些波的色球能量通量估计为≈3 × 105 W m−2，这表明它们的能量足以加速太阳风并将局部日冕加热到数百万度的温度。
We use images of high spatial and temporal resolution, obtained with the Rapid Oscillations in the Solar Atmosphere instrument at the Dunn Solar Telescope, to reveal how the generation of transverse waves in Type I spicules is a direct result of longitudinal oscillations occurring in the photosphere. Here we show how pressure oscillations, with periodicities in the range of 130–440 s, manifest in small-scale photospheric magnetic bright points, and generate kink waves in the Sun's outer atmosphere with transverse velocities approaching the local sound speed. Through comparison of our observations with advanced two-dimensional magnetohydrodynamic simulations, we provide evidence for how magnetoacoustic oscillations, generated at the solar surface, funnel upward along Type I spicule structures, before undergoing longitudinal-to-transverse mode conversion into waves at twice the initial driving frequency. The resulting kink modes are visible in chromospheric plasma, with periodicities of 65–220 s, and amplitudes often exceeding 400 km. A sausage mode oscillation also arises as a consequence of the photospheric driver, which is visible in both simulated and observational time series. We conclude that the mode conversion and period modification is a direct consequence of the 90° phase shift encompassing opposite sides of the photospheric driver. The chromospheric energy flux of these waves are estimated to be ≈3 × 105 W m−2, which indicates that they are sufficiently energetic to accelerate the solar wind and heat the localized corona to its multi-million degree temperatures.