Coronal Mass Ejections (CMEs) are large-scale eruptions in the Sun, accompanied by big amounts of mass and energy release. It has been shown that the major geomagnetic storms are caused by CMEs. Therefore, the research on CMEs is important for the space weather. Since the launch of the twin STEREO spacecraft, many progresses have been made, especially on the 3D reconstructions of CMEs to remove the projection effect. It provides valuable information on the CME propagation direction and speed which are important for the geo-effectiveness.

In a published paper in Solar Physics by Dr. Li Feng and her collaborators, a couple of methods on 3D reconstructions of CMEs have been compared with the mask fitting method recently developed by the same author, especially in the propagation direction of a CME and its spatial extent in 3D. It’s found that the derived CME longitude differs between various methods, while the CME latitude is generally consistent.

Through the method comparisons, the authors found that the mask fitting method which takes advantage of three different views produces more precise results. The previous methods were often based on observations from two views. It can also be applicable to CMEs with any kind of shape which is not necessary a flux rope. Therefore, the mask fitting method is more flexible. For more details of this work, please check the link:http://link.springer.com/article/10.1007%2Fs11207-012-0143-1 (Solar Physics, 2013, Vol 282, Issue 1, pp 221-238).

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

Top view of the reconstructed 3D CMEs. Red curves are produced by the mask fitting method. Green and yellow are from the polarization ratio meothod.

　　　　　By with FENG Li

The 3D CME from the mask fitting method (black) compared with the flux rope shape CME (red).