Recently, we have developed a method useful for mapping large-scale horizontal velocity fields in the solar photosphere. The method was developed, tuned and calibrated using the synthetic data. Now, we applied the method to the series of Michelson Doppler Imager (MDI) dopplergrams covering almost one solar cycle in order to get the information about the long-term behaviour of surface flows. We have found that our method clearly reproduces the widely accepted properties of mean flow field components, such as torsional oscillations and a pattern of meridional circulation. We also performed a periodic analysis, however due to the data series length and large gaps we did not detect any significant periods. The relation between the magnetic activity influencing the mean zonal motion is studied. We found an evidence that the emergence of compact magnetic regions locally accelerates the rotation of supergranular pattern in their vicinity and that the presence of magnetic fields generally decelerates the rotation in the equatorial region. Our results show that active regions in the equatorial region emerge exhibiting a constant velocity (faster by 60 +/- 9 m/s than Carrington rate) suggesting that they emerge from the base of the surface radial shear at 0.95 R_sun, disconnect from their magnetic roots, and slow down during their evolution.
The horizontal internetwork magnetic field: numerical simulations in comparison to observations with Hinode
日之出空间天文台的观测结果是,在平静的互联网区域的光球层中发现了主要是水平的磁场。在这里,我们调查现实的数值模拟的太阳表面层相对于水平磁场和计算相应的偏振响应在Fe I 630 nm线对。我们发现一个局部最大值的水平场分量的平均强度在一个高度约500公里的光球,在那里它超过垂直分量的一个因素为2.0或5.6,这取决于初始和边界条件。从合成的斯托克斯配置文件,我们得到一个平均水平场分量,分别是1.6和4.3倍强于垂直分量。这是由于水平场本身的通量密度更强,并且水平场占据的面积更大。我们发现,对流过冲驱逐水平场的上层光球,使坡印亭通量为正的光球,而这个量是负的对流不稳定层下面。
Small-scale fluctuations of magnetic field and velocity may be responsible for the Stokes asymmetries observed in all photospheric magnetic structures (the MISMA hypothesis). We support the hypothesis showing that atmospheres with optically-thin micro-structure reproduce the polarization of FeI 6301 A and FeI 6302 A observed in a sunspot. Ten thousand spectra were fitted by model MISMAs with two magnetic components interleaved along the line-of-sight. Combining all the fits, we set up a semi-empirical model sunspot characterized by two components with very different magnetic field inclination.…
Influence of atomic polarization and horizontal illumination on the Stokes profiles of the He I 10830 multiplet
在He I 10830多重态谱线中观察到的偏振态携带着太阳色球和日冕中等离子体结构的动力学和磁性质的有价值的信息,如针状体、双折射体、丝状体、新兴磁通区等。在这里,我们研究了原子水平偏振对大范围磁场强度的新兴斯托克斯轮廓的影响,在90度和前向散射几何结构中。我们发现,与普遍认为的相反,原子级偏振的存在所引起的选择性发射和吸收过程可能对出射线偏振产生重要影响,即使磁场强度高达1000 G。因此,Stokes Q和U分布的建模不应仅考虑Paschen-Back效应理论框架内的横向塞曼效应的贡献,除非观察到的等离子体结构的磁场强度明显大于1000 G。我们还指出,在低洼的光学厚等离子体结构,如那些活跃的区域灯丝,(水平)辐射场产生的结构本身可能会大大减少积极的贡献所造成的(垂直)辐射场来自下面的太阳光球的各向异性因子,使原子级偏振的量可能会变成可以忽略不计。只有在这种情况下,在太阳大气的这些区域中,He I 10830多重态的出射线偏振才可能由横向塞曼效应所引起的贡献所主导。
Explanation of the activity sensitivity of Mn I 5394.7 Å
关于太阳辐照度谱中Mn I 5394.7 A谱线在大活动时比大多数其他光球谱线更亮的原因,长期存在争议。这种活动敏感性是由Mg II h & k的色球发射光谱联锁引起的说法是有争议的。采用经典的一维建模方法进行论证,采用现代的三维磁流体模拟方法进行验证和分析。Mn I 5394.7 A谱线对太阳活动异常敏感,这要归功于它的超精细结构。这就克服了其他较窄的光球线失去这种灵敏度的热多普勒拖尾效应和颗粒多普勒拖尾效应。我们以邻近的Fe I 5395.2 A线为例,详细分析了这两条线的形成,以证明和解释颗粒多普勒增亮。我们表明,这会影响所有的窄线。无论是色球,也没有Mg II H & K发挥的作用,也是不正确的描述活动的灵敏度Mn I 5394.7 A通过plage模型与向外增加的温度对比。Mn I 5394.7 A线代表了太阳光球层深处强磁场浓度的代用诊断,与G波段和H-α的蓝翼相当,但不是比这些更好的。Mn I线在高分辨率Stokes偏振测量中作为弱场的诊断更有前途。