A magnetically-driven model of flux-rope expansion from the Sun to 1AU in order to compute Bz at 1AU.

We will present the results of the HelioXM model that simulates the propagation of CME magnetic flux ropes from the Sun to the Earth by including both the dynamics of the apex and the legs of the flux ropes. Therefore the model calculates the expansion of a flux rope in three orthogonal directions based on physical forces: apex expansion, transverse expansion, and minor radial expansion. The model provides two important predictions: (1) estimates of the magnetic field strength and orientation of the CME Bz component at 1AU (2) estimates of the arrival time of the magnetized CME ejecta. The model calculates the evolving magnetic field inside the CME ejecta (in three dimension Bx, By, Bz) in relation to the initial geometry of the CME at the Sun and height-time data measured directly in white-light images. We present an application based on this type of model that computes the magnetic field vector components seen by a probe/planet traversing the CME for any orientation of the flux rope.