Oscillations in a network region observed in the Hα line and their relation to the magnetic field
Oscillations in a network region observed in the Hα line and their relation to the magnetic field
复制标题
Hα 线中观察到的网络区域的振荡及其与磁场的关系
DOI：
--
复制
发表时间：
2010
期刊：
影响因子：
--
通讯作者：
M. Georgoulis
中科院分区：
文献类型：
--
作者：
I. Kontogiannis;G. Tsiropoula;K. Tziotziou;M. Georgoulis
目标。我们的目标是更好地了解声波振荡和太阳小尺度磁场之间的相互作用。为此，我们研究了网络区域的振荡特性及其与色球磁结构的关系。我们链接的振荡特性的网络区域和它们的空间变化与磁场的参数的变化。我们研究了色球网络的磁冠和发散通量管对振荡功率在网络和网络间分布的影响。方法.我们使用的时间序列的高分辨率滤波图在五个波长沿着的Hα剖面观察到的荷兰开放望远镜，以及高分辨率磁图所采取的SOT/SP机载HINODE。利用小波分析方法，分别在距Hα线中心± 0.35A和± 0.7A处计算了多普勒信号3、5和7 min振荡的功率图。它们分别代表色球层和光球层的速度。通过无电流（位）场外推，我们计算了色球磁场，并将其形态与Hα滤波图进行了比较。我们计算了等离子体β和磁场倾角，并比较了它们的分布和振荡功率在3、5和7 min周期带的分布。结果色球斑似乎勾勒出了磁力线。Hα ± 0.35A多普勒信号在冠层上方形成，Hα ± 0.7A多普勒信号在冠层下方形成，在1600 km以下的色球层，3 min功率被抑制，而在光球层，由于反射，3 min功率被增强。在光球层，由于波在上覆林冠上的反射，网周围的3、5和7 min振荡功率增加，而在色球层，增加的5和7 min功率主要归因于林冠上的波折射。在这些高周期，由于磁场的高倾斜，功率也由于p模式泄漏而增加。结论.我们的高分辨率Hα观测和光球磁图提供了一个机会，突出的声学振荡和网络区域的磁场之间的相互作用的细节。我们的结论是，已经提出的几种机制，如p-模式泄漏，模式转换，反射和折射的磁冠波可能会共同作用，并导致观察到的网络振荡的性质。
Aims. Our aim is to gain a better understanding of the interaction between acoustic oscillations and the small-scale magnetic fields of the Sun. To this end, we examine the oscillatory properties of a network region and their relation to the magnetic configuration of the chromosphere. We link the oscillatory properties of a network region and their spatial variation with the variation of the parameters of the magnetic field. We investigate the effect of the magnetic canopy and the diverging flux tubes of the chromospheric network on the distribution of oscillatory power over the network and internetwork. Methods. We use a time series of high resolution filtergrams at five wavelengths along the Hα profile observed with the Dutch Open Telescope, as well as high resolution magnetograms taken by the SOT/SP onboard HINODE. Using wavelet analysis, we construct power maps of the 3, 5 and 7 min oscillations of the Doppler signals calculated at ±0.35 A and ±0.7 A from the Hα line center. These represent velocities at chromospheric and photospheric levels respectively. Through a current-free (potential) field extrapolation we calculate the chromospheric magnetic field and compare its morphology with the Hα filtergrams. We calculate the plasma β and the magnetic field inclination angle and compare their distribution with the oscillatory power at the 3, 5 and 7 min period bands. Results. Chromospheric mottles seem to outline the magnetic field lines. The Hα ± 0.35 A Doppler signals are formed above the canopy, while the Hα ± 0.7 A corresponding ones below it. The 3 min power is suppressed at the chromosphere around the network, where the canopy height is lower than 1600 km, while at the photosphere it is enhanced due to reflection. 3, 5 and 7 min oscillatory power is increased around the network at the photosphere due to reflection of waves on the overlying canopy, while increased 5 and 7 min power at the chromosphere is attributed mainly to wave refraction on the canopy. At these high periods, power is also increased due to p-mode leakage because of the high inclinations of the magnetic field. Conclusions. Our high resolution Hα observations and photospheric magnetograms provide the opportunity to highlight the details of the interaction between acoustic oscillations and the magnetic field of a network region. We conclude that several mechanisms that have been proposed such as p-mode leakage, mode conversion, reflection and refraction of waves on the magnetic canopy may act together and result to the observed properties of network oscillations.