Estimation of Arrival Time of Coronal Mass Ejections in the Vicinity of the Earth Using SOlar and Heliospheric Observatory and Solar TErrestrial RElations Observatory Observations

Abstract

The arrival time of coronal mass ejections (CMEs) in the vicinity of the Earth is one of the most important parameters in determining space weather. We have used a new approach to predicting this parameter. First, in our study, we have introduced a new definition of the speed of ejection. It can be considered as the maximum speed that the CME achieves during the expansion into the interplanetary medium. Additionally, in our research we have used not only observations from the SOlar and Heliospheric Observatory (SOHO) spacecraft but also from Solar TErrestrial RElations Observatory (STEREO) spacecrafts. We focus on halo and partial halo CMEs during the ascending phase of Solar Cycle 24. During this period the STEREO spacecraft were in quadrature position in relation to the Earth. We demonstrated that these conditions of the STEREO observations can be crucial for an accurate determination of the transit times (TTs) of CMEs to the Earth. In our research we defined a new initial velocity of the CME, the maximum velocity determined from the velocity profiles obtained from a moving linear fit to five consecutive height time points. This new approach can be important from the point of view of space weather as the new parameter is highly correlated with the final velocity of ICMEs. It allows one to predict the TTs with the same accuracy as previous models. However, what is more important is the fact that the new approach has radically reduced the maximum TT estimation errors to 29 hours. Previous studies determined the TT with a maximum error equal to 50 hours.