五种三维重建方法提取的CME形态特征比较
Comparisons of CME morphological characteristics derived from five 3D reconstruction methods
摘要：
我们比较不同的方法来重建的三维（3D）CME形态。探索的方法包括几何定位，掩模拟合，正演模拟，极化比和局部相关跟踪加三角测量。这五种方法适用于同一个CME事件，发生在2010年8月7日。给出了它们的相应结果，并进行了比较，特别是在它们的三维传播方向和空间范围方面。我们发现，掩模拟合和几何定位方法产生一致的结果。包括三视图观察的重建比仅用两个视图进行的重建更精确。与假定CME几何形状先验的正演模拟方法相比，掩模拟合具有更大的灵活性。偏振比方法利用汤姆逊散射几何。在空间上，我们发现由掩模拟合得到的三维CME主要位于由COR 2 A和B的偏振方法得到的重叠区域。此外，掩模拟合可以帮助解决偏振比方法中固有的前/后模糊性。然而，局部相关跟踪加三角剖分并没有显示出与其他四种方法一致的结果。对于漫射CME的重建，当STEREO A和B之间的分离角较大时，在STEREO图像对中找到两个对应点变得非常困难。除局部相关跟踪法外，其他方法得到的日冕物质抛射重心纬度偏差在1度以内，经度偏差在19度以内。
英文摘要：
We compare different methods to reconstruct the three-dimensional (3D) CME morphology. The explored methods include geometric localisation, mask fitting, forward modeling, polarisation ratio and local correlation tracking plus triangulation. The five methods are applied to the same CME event, which occurred on August 7 2010. Their corresponding results are presented and compared, especially in their propagation direction and spatial extent in 3D. We find that mask fitting and geometric localisation method produce consistent results. Reconstructions including three-view observations are more precise than reconstructions done with only two views. Compared to the forward modeling method, in which a-priori shape of the CME geometry is assumed, mask fitting has more flexibility. Polarisation ratio method makes use of the Thomson scattering geometry. We find spatially the 3D CME derived from mask fitting lies mostly in the overlap region obtained with the polarisation method from COR2 A and B. In addition, mask fitting can help resolve the front/back ambiguity inherent in the polarisation ratio method. However, local correlation tracking plus triangulation did not show a consistent result with the other four methods. For reconstructions of a diffuse CME, when the separation angle between STEREO A and B is large, finding two corresponding points in a STEREO image pair becomes very difficult. Excluding the local correlation tracking method, the latitude of the CME's centre of gravity derived from the other methods deviates within one degree and longitude differs within 19 degrees.
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