Influence of Convection Effects of Solar Wind Speed on CME Transit Time

Based on the experiential predicting model, 52 CME events which cause geomagnetic storms Dst< -50nT, and 10 CME events which cause significant geomagnetic storms (Dst< -200nT) in 1996-2007 are selected, and mix with the observation data of interplanetary solar wind and ICME that are collected by ACE satellite at 1AU, convection effects of ambient solar wind speed on the CME transit time from the Sun to the Earth are analyzed. The results show that significant improvement on the predicting transit time of CME events after taking the convection effects into account has been obtained. For the 52 CME events of Dst< -50nT, the prediction standard difference is reduced from 16.5 to 11.4 hours, and the prediction error is less than 15 hours for 68% of these events. For the 10 CME events (Dst< -200nT), the prediction standard difference is reduced from 10.6 to 6.5 hours. Furthermore, the prediction error of 6 events among these 10 events is less than 5 hours. The study identifies the importance of convection effects of solar wind speed on the prediction of CME transit time.