We analyse the topology of photospheric magnetic fields and sub-photospheric flows of several active regions (ARs) that are observed during the peak to descending phase of the solar cycle 23. Our analysis shows clear evidence of hemispheric preferences in all the topological parameters such as the magnetic, current and kinetic helicities, and the 'curl-divergence'. We found that 68\%(67\%) ARs in the northern (southern) hemisphere with negative (positive) magnetic helicities. Same hemispheric preference sign is found for the current helicities in 68\%(68\%) ARs. The hemispheric preferences are found to exist statistically for all the time except in few ARs observed during the peak and the end phases of the solar cycle. This means that magnetic fields are dominantly left(right)-helical in scales smaller than individual ARs of northern(southern) hemisphere. We found that magnetic and current helicities parameters show equator-ward propagation similar to the sunspot cycle. The kinetic helicity showed similar hemispheric trend to that of magnetic and current helicity parameters. There are 65\%(56\%) ARs with negative (positive) kinetic helicity as well as divergence-curl, at the depth of 2.4\,Mm, in the northern (southern) hemisphere. The hemispheric distribution of the kinetic helicity becomes more evident at larger depths, e.g., 69\%(67\%) at the depth of 12.6\,Mm. Similar hemispheric trend of kinetic helicity to that of the current helicity supports the mean field dynamo model. We also found that the hemispheric distribution of all the parameters increases with the field strength of ARs. The topology of photospheric magnetic fields and near surface sub-photospheric flow fields did not show good association but the correlation between them enhances with depths which could be indicating more aligned flows at deeper layers of ARs.

中文翻译：

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太阳活动周期下降阶段活动区的磁场和速度场拓扑结构 23

我们分析了在太阳活动周期的高峰到下降阶段观察到的几个活动区域 (AR) 的光球磁场和亚光球流的拓扑结构 23。我们的分析显示了所有拓扑参数中半球偏好的明确证据，例如磁、电流和动力学螺旋，以及“卷曲发散”。我们发现北（南）半球的 68\%（67\%）个 AR 具有负（正）磁螺旋。在 68\%(68\%) ARs 中发现了相同的半球偏好符号。发现半球偏好在统计上一直存在，除了在太阳周期的高峰和结束阶段观察到的少数 AR。这意味着磁场在比北（南）半球的单个 AR 更小的尺度上主要是左（右）螺旋。我们发现磁力和电流螺旋度参数显示出类似于太阳黑子周期的赤道向传播。动力学螺旋度显示出与磁性和电流螺旋度参数相似的半球趋势。在北（南）半球 2.4\,Mm 深度处，有 65\%（56\%）个具有负（正）动力学螺旋度和发散卷曲的 AR。动力学螺旋的半球分布在较大深度处变得更加明显，例如在12.6\,Mm 深度处为69\%(67\%)。动力学螺旋的半球趋势与当前螺旋的类似，支持平均场发电机模型。我们还发现所有参数的半球分布随着 AR 的场强而增加。光球磁场和近地表亚光球流场的拓扑结构没有显示出良好的关联，但它们之间的相关性随着深度的增加而增强，这可能表明在更深的 AR 层有更多的对齐流。