用Magnetic Induction方程跟踪矢量磁图
Tracking Vector Magnetograms with the Magnetic Induction Equation
摘要：
Schuck（2006）开发的用于从视线磁图估计速度的差分仿射速度估计器（DAVE）被修改为直接并入水平磁场以产生用于矢量磁图的差分仿射速度估计器（DAVE 4VM）。DAVE 4VM的性能在来自滞弹性伪谱ANMHD模拟的合成数据上得到了证明，该模拟用于Welsch（2007）最近的速度反演技术比较。DAVE 4VM预测大约95%的螺旋率和75%的通过模拟切片传输的功率。DAVE 4VM和DAVE之间的相互比较和DAVE方法的进一步分析表明，视线跟踪方法捕获磁足点的剪切运动，但对磁通量出现不敏感-从视线方法确定的速度与水平等离子体速度比与磁通量传输速度更一致。这些结果表明，以前的研究，依赖于从视线的方法，如DAVE或本地相关跟踪确定的速度可能会大大歪曲总螺旋率和功率通过光球。
英文摘要：
The differential affine velocity estimator (DAVE) developed in Schuck (2006) for estimating velocities from line-of-sight magnetograms is modified to directly incorporate horizontal magnetic fields to produce a differential affine velocity estimator for vector magnetograms (DAVE4VM). The DAVE4VM's performance is demonstrated on the synthetic data from the anelastic pseudospectral ANMHD simulations that were used in the recent comparison of velocity inversion techniques by Welsch (2007). The DAVE4VM predicts roughly 95% of the helicity rate and 75% of the power transmitted through the simulation slice. Inter-comparison between DAVE4VM and DAVE and further analysis of the DAVE method demonstrates that line-of-sight tracking methods capture the shearing motion of magnetic footpoints but are insensitive to flux emergence -- the velocities determined from line-of-sight methods are more consistent with horizontal plasma velocities than with flux transport velocities. These results suggest that previous studies that rely on velocities determined from line-of-sight methods such as the DAVE or local correlation tracking may substantially misrepresent the total helicity rates and power through the photosphere.
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