论文标题
太阳表面剪切层中差异旋转和子午流的变化1996-2022
Variations in Differential Rotation and Meridional Flow within the Sun's Surface Shear Layer 1996-2022
论文作者
论文摘要
我们通过跟踪SOHO/MDI和SDO/HMI在太阳能周期上在太阳周期23、24和25的开始(1996-2022)中的磁力图中观察到的磁网络的运动,测量太阳表面剪切层中的差分旋转和子午流。我们检查了从单个27天的卡灵顿旋转中平均每天15-24个测量结果得出的轴对称流。差异旋转的变化包括赤道扭转振荡 - 旋风流以活跃纬度的中心为中心,在活性纬度的极侧流较慢,并且赤道更快。快速流频段以$ \ sim $ 45 $^\ circ $ latitude在上一个周期的下降阶段开始,并漂移赤道,在最小周期的最低限度时终止了赤道。差异旋转的变化还包括高于45 $^\ circ $的极性振荡,在周期最大值时旋转速度更快,并且在循环最小值时旋转较慢。在周期24中,赤道变化比周期23中的变化更强,但极性变化较弱。子午流的变化包括在循环上升和最大值期间活跃纬度中极流的减慢,以及在循环下降和最小值期间的极点升高。在周期24中,活动纬度的放缓不如周期23中的明显。极性反病(赤道流)从杆子延伸到$ \ sim $ 60 $^\ CIRC $时不时(1996-2000和2016-000和2016-2022在南部以及北部的2001-2011和2017-2011和2017-2022)。两种轴对称流的强度都随深度而变化。旋转速率向内增加,而子午流量向内削弱。
We measure differential rotation and meridional flow in the Sun's surface shear layer by tracking the motions of the magnetic network seen in magnetograms from SOHO/MDI and SDO/HMI over solar cycles 23, 24, and the start of 25 (1996-2022). We examine the axisymmetric flows derived from 15-24 daily measurements averaged over individual 27-day Carrington rotations. Variations in the differential rotation include the equatorial torsional oscillation - cyclonic flows centered on the active latitudes with slower flows on the poleward sides of the active latitudes and faster flows equatorward. The fast flow band starts at $\sim$45$^\circ$ latitude during the declining phase of the previous cycle and drifts equatorward, terminating at the equator at about the time of cycle minimum. Variations in the differential rotation also include a polar oscillation above 45$^\circ$ with faster rotation at cycle maxima and slower rotation at cycle minima. The equatorial variations were stronger in cycle 24 than in cycle 23 but the polar variations were weaker. Variations in the meridional flow include a slowing of the poleward flow in the active latitudes during cycle rise and maximum and a speeding up of the poleward flow during cycle decline and minimum. The slowing in the active latitudes was less pronounced in cycle 24 than in cycle 23. Polar countercells (equatorward flow) extend from the poles down to $\sim$60$^\circ$ latitude from time to time (1996-2000 and 2016-2022 in the south and 2001-2011 and 2017-2022 in the north). Both axisymmetric flows vary in strength with depth. The rotation rate increases inward while the meridional flow weakens inward.