Forward Modeling of Coronal Mass Ejections Using STEREO/SECCHI Data

We describe a forward modeling method developed to study the coronal mass ejections observed with STEREO/SECCHI. We present a survey of 26 CMEs modeled with this method. We selected most of the bright events observed since November 2007 to August 2008, after when the separation was greater than 40° degrees, thus showing noticeable differences between the two views. From these stereoscopic observations and using a geometric model of a flux rope, we are able to determine the three-dimensional direction of propagation, the three-dimensional velocity and acceleration of the CME front, and in most of the cases the flux rope orientation and length. We define a merit function that allows us to partially automate the fit, as well as perform a sensitivity analysis on the model parameters. We find a precision on the longitude and latitude to be of a maximum of ±17° and ±4°, respectively, for a 10% decrease of the merit function but a precision on the flux rope orientation and length to be almost one order of magnitude larger, showing that these parameters are more difficult to estimate using only coronagraph data. Finally, comparison with independent measurements shows a good agreement with the direction and speed we estimated.