We present unprecedented high-resolution TiO images and Fe i 1565 nm spectropolarimetric data of two light bridges taken by the 1.6 m Goode Solar Telescope at Big Bear Solar Observatory. In the first light bridge (LB1), we find striking knot-like dark structures within the central dark lane. Many dark knots show migration away from the penumbra along the light bridge. The sizes, intensity depressions, and apparent speeds of their proper motion along the light bridges of 33 dark knots identified from the TiO images are mainly in the ranges of 80?~?200?km, 30%?~?50%, and 0.3?~?1.2 km s?1, respectively. In the second light bridge (LB2), a faint central dark lane and striking transverse intergranular lanes were observed. These intergranular lanes have sizes and intensity depressions comparable to those of the dark knots in LB1 and also migrate away from the penumbra at similar speeds. Our observations reveal that LB2 is made up of a chain of evolving convection cells, as indicated by patches of blueshift surrounded by narrow lanes of redshift. The central dark lane generally corresponds to blueshifts, supporting the previous suggestion of central dark lanes being the top parts of convection upflows. In contrast, the intergranular lanes are associated with redshifts and located at two sides of each convection cell. The magnetic fields are stronger in intergranular lanes than in the central dark lane. These results suggest that these intergranular lanes are manifestations of convergent convective downflows in the light bridge. We also provide evidence that the dark knots observed in LB1 may have a similar origin.
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机译:我们提供了史无前例的高分辨率TiO图像以及由大熊太阳能天文台的1.6 m古德太阳望远镜拍摄的两个光桥的Fe i 1565 nm光谱极化数据。在第一个光桥(LB1)中,我们在中央黑暗车道内发现了醒目的类似结的黑暗结构。许多暗结显示出沿着光桥从半影中移出。从TiO图像中识别出的33个暗结的光桥的大小,强度降低和适当运动的视在速度主要在80?〜?200?km,30%?〜?50%和0.3的范围内分别为〜1.2km s·1。在第二个光桥(LB2)中,观察到微弱的中央暗车道和醒目的横向晶间车道。这些粒间泳道的大小和强度降低程度可与LB1中的暗结相媲美,并且以相似的速度从半影中移走。我们的观察结果表明,LB2由不断发展的对流细胞链组成,如蓝移斑块和红移窄道所包围。中央暗线通常对应于蓝移,支持先前关于中央暗线为对流上升流顶部的建议。相反,晶间泳道与红移相关联并且位于每个对流单元的两侧。晶间通道中的磁场比中央暗通道中的磁场强。这些结果表明,这些晶间通道是轻桥中对流向下汇流的表现。我们还提供了证据,表明在LB1中观察到的暗结可能起源相似。
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