Prediction of CME arrivals; differences based on stereoscopic heliospheric imager data

Forecasting the arrival time and speed of CMEs is of high importance. However, uncertainties in the forecasts are high. We present the results of post-event prediction of CME arrivals using ELEvoHI (ELlipse Evolution model based on Heliospheric Imager observations) ensemble modeling. The model uses time-elongation profiles provided by HI (Heliospheric Imager) onboard STEREO (Solar TErrestrial RElations Observatory) and assumes an elliptical shape of the CME front. The drag force exerted by the ambient solar wind is an essential factor influencing the dynamic evolution of CMEs in the heliosphere. To account for this effect, ELEvoHI utilizes the modeled ambient solar wind provided by the Wang-Sheeley-Arge model. We carefully select 12 CMEs between February 2010 and July 2012, which show clear signatures in STEREO-A and STEREO-B HI images, have a corresponding in-situ signature, and propagate close to the ecliptic plane. As input to ELEvoHI, we make use of STEREO-A and STEREO-B time-elongation profiles for each CME and compare the predicted arrival times and speeds based on both vantage points with each other. We present our model results and discuss possible reasons for the differences in the arrival times of up to 15 hours.