Testing Capability of CME Eccentricity Parameter

Rho et al.(2008) showed that the eccentricity parameter of a CME is an important indicator for forecasting CME geoeffectiveness. In this study we have tested a capability of the eccentricity parameter as an indicator of CME direction. For this work we considered 11 CMEs observed by both SOHO/LASCO and STEREO/SECCHI (2007-2008 from Temmer et al. 2009) coronagraphs. We have estimated earthward direction angles for these CMEs based on two different methods: (1) the eccentricity parameter from a single coronagraph SOHO/LASCO and (2) the triangulation technique using a pair of spacecrafts LASCO/STEREO-A and LASCO/STEREO-B. As a result, we have found that for 7 out of 11 CME events their direction angles are consistent with each other within $20^{\circ}$. This result demonstrates that the earthward direction based on the eccentricity parameter can be a good potential indicator for CME propagation direction.