Coronal Mass Ejections (CMEs) are large-scale eruptions in the Sun, accompanied by big amounts of mass and energy release. The research on CMEs is an important branch of space weather. The SOHO satellite launched in 1995 has produced lots of observations on CMEs. However, most of the studies on CMEs have been limited to two dimensions. The projection effect has made SOHO data imperfect in the estimation of the CME arrival time in the Earth, especially to halo CMEs.

At the end of 2006, two almost identical spacecraft were launched by USA in the STEREO mission. Dr. Li Feng and her collaborators developed a new technique to obtain the three-dimensional (3D) morphology of CMEs from the white-light coronagraph images observed by STEREO and SOHO (see Figs. 1 and 2). The reconstructed 3D CME can determine its propagation direction, particularly, if it has some possibility to arrive any planet in the solar system. Together with the observations made by the SDO satellite, the authors investigated the characteristics in the source region of the CME.

In addition, the CME-related data from the planetary spacecraft have been explored. The authors compared the 3D morphology of the CME and the data on the interplanetary CME (ICME) produced by Venus Express. It shows that the 3D CME can interpret very well the magnetic field observations by Venus Express. The evolution of the CME in the interplanetary space has also been studied. The aforementioned work will be published by Astrophysics Journal. More details can be found by following the link http://arxiv.org/abs/1203.3261.

（by FENG Li）

Fig. 1: The black sphere represents the Sun, and red curves localize the 3D CME. Based on the 3D CME morphology, its geometric center (a green sphere) and three principle (three solid black lines) axes are calculated.

（by FENG Li）

Fig. 2: The projection of the 3D CME on the solar equatorial plane. Its localization with respect to the view direction of two STEREO spacecraft (STA, STB), Venus and Earth can be utilized to determine if it arrives any planet.