Evidence for the emergence of twisted flux tubes into the solar atmosphere has, so far, come from indirect signatures. In this work, we investigate the topological input of twisted flux tube emergence directly by studying helicity and winding fluxes. In magnetohydrodynamic simulations with domains spanning from the top of the convection zone to the lower corona, we simulate the emergence of twisted flux tubes with a range of different initial field strengths. One important feature of this work is the inclusion of a convectively unstable layer beneath the photosphere. We find approximately self-similar behaviour in the helicity input for the different field strengths considered. As the tubes rise and reach the photosphere, there is a strong input of negative helicity since we consider left-handed twisted tubes. This phase is then followed by a reduction of the negative input and, for low initial field strengths, a net positive helicity input. This phase corresponds to the growing influence of convection on the field and the development of serpentine field structures during emergence. The winding flux can be used to detect when the twisted cores of the tubes reach the photosphere, giving clear information about the input of topologically complex magnetic field into the solar atmosphere. In short, the helicity and winding fluxes can provide much information about how a magnetic field emerges that is not directly available from other sources, such as magnetograms. In evaluating the helicity content of these simulations, we test numerous means for creating synthetic magnetograms, including methods which account for both the evolving geometry and the finite extent of the photosphere. Whilst the general qualitative behaviours are similar in each case, the different forms of averaging do affect the helicity and winding inputs quantitatively.

中文翻译：

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螺旋度和绕组通量作为扭曲通量出现的指标

迄今为止，扭曲的通量管出现在太阳大气中的证据来自间接特征。在这项工作中，我们通过研究螺旋度和绕组通量来直接研究扭曲通量管出现的拓扑输入。在磁流体动力学模拟中，域从对流区顶部到下部日冕，我们模拟了具有一系列不同初始场强的扭曲磁通管的出现。这项工作的一个重要特点是在光球层下方包含了一个对流不稳定的层。对于所考虑的不同场强，我们在螺旋度输入中发现了近似自相似的行为。当管上升并到达光球层时，由于我们考虑左旋扭曲管，因此存在强烈的负螺旋输入。这个阶段之后是负输入的减少，对于低初始场强，净正螺旋度输入。这一阶段对应于对流对场的影响越来越大，以及出现期间蛇形场结构的发展。绕组通量可用于检测管子的扭曲芯何时到达光球层，从而提供有关拓扑复杂磁场输入到太阳大气中的清晰信息。简而言之，螺旋度和绕组磁通可以提供很多关于磁场如何出现的信息，而其他来源（例如磁力图）无法直接获得这些信息。在评估这些模拟的螺旋含量时，我们测试了多种创建合成磁力图的方法，包括解释不断变化的几何形状和光球的有限范围的方法。虽然在每种情况下一般的定性行为都相似，但不同形式的平均确实会定量地影响螺旋度和缠绕输入。