MHD numerical study of coronal mass ejection and its latitudinal deflection

To predict whether or not a CME can arrive on the Earth and its IMF Bz are an important topic for space weather study. Here, we analyze the latitudinal deflection (LD) of CME during its propagation by using our 3D SIP-CESE MHD model. A spherical plasmoid CME model is used to mimic the 12 May 1997 event, with the CME being assumed at the observed location to arise from the evolution of a spheromak magnetic structure with high-speed, -pressure, and -density plasmoid. The result produced a relatively satisfactory comparison with Wind, such as southward IMF Bz. The effect of the background magnetic field and the initiation parameters on the LD CMEs show that the parallel CMEs (with CME's initial magnetic field parallel to that of the ambient field) at high latitude show an obvious equatorward deflection firstly, and then propagate almost parallel to HCS, while the anti-parallel CMEs deflect toward the pole. The LD extent of parallel CMEs are mainly controlled by the background magnetic field strength, and the initial magnetic field strength of CMEs. There is an anti-relation between the LD extent and the CME average transit speed and the energy ratio Ecme/Esw. Three dimensional view of the initial coronal magnetic field. Field lines of the CME are shown in color to illustrate the magnetic field strength. The color contours represent the radial magnetic field strength on the solar surface.

Comparison between the in situ obtained by the WIND and our simulation during the 12 May 1997 event. From top to bottom, shown are flow velocity, number density, magnetic field, and three components of magnetic field in GSE coordinates. The simulated results at the Earth are shown by solid lines. The WIND observations are shown by dots.