Forecasting interplanetary ejecta arrival at 1 AU

A big challenge in space weather forecasting is the prediction of arrival of an interplanetary disturbance at earth. Many attempts have been done, and some forecasting models have been proposed. We focus on the subset of solar-interplanetary events which have shown interplanetary ejecta at 1 AU. To identify interplanetary ejecta at 1 AU we use visual inspection of the cases, based on the criterion of intense and smooth magnetic field, observed by the Advanced Composition Explorer (ACE). For forecasting the arrival of the interplanetary ejecta at 1 AU we used the lateral expansion speed of the coronal mass ejection, measured approximately perpendicular to the single plane-of-sky CME speed, as defined by Schwenn et al (2001), using observations from the Large Angle and Spectroscopic Coronagraph (LASCO), aboard the Solar and Heliospheric Observatory (SOHO). The data set is from January 1997 to mid April 2001, and a number of 38 LASCO CMEs were identified to be correlated with interplanetary ejecta at 1 AU. Results indicate that forecasting the arrival at 1 AU of the sub set of interplanetary ejecta is very well done by LASCO CME speed observations, being much better than the predictions for the complete set of interplanetary disturbances, like shocks/sheath structures.