Validating a new method for deriving the kinematics of ICMEs with a numerical simulation

Using a numerical simulation of a very wide coronal mass ejection (CME) we validate a method for calculating propagation directions and kinematical profiles of interplanetary CMEs (ICMEs). In this method observations from heliospheric images are constrained with the in-situ arrival time at 1 AU. This additional boundary condition is used to calculate the propagation direction and to convert measured ICME elongations into distance by applying the Harmonic Mean approach that assumes a spherical shape of the ICME front. We use synthetic white light images, similar as observed by STEREO-A/HI, for three different separation angles between remote and in-situ spacecraft, of 30°, 60° and 90°. For validation, the results of the method are compared to the "true" speed profile of the modeled ICME, as obtained from top view density images, for every separation case. In this way it is possible to determine the accuracy of the method for revealing ICME propagation directions and kinematics. We found that the direction yield by the constrained Harmonic Mean method is not very sensitive on the separation angle. For all three cases the derived kinematics are in a relatively good agreement with the real kinematics. The best consistency is obtained for the 30° case, while with growing separation the ICME speed at 1 AU is increasingly overestimated. Especially for future L4/L5 missions the 60° separation case is highly interesting in order to improve space weather forecasts.