Numerical Simulations on the Deflection of Coronal Mass Ejections in the Interplanetary Space

Deflection of coronal mass ejections (CMEs) in the interplanetary space, especially in the ecliptic plane, serves as an important factor deciding whether CMEs arrive at the Earth. Observational studies have shown evidence for deflection, whose detailed dynamic processes, however, remain obscure. Here we developed a 2.5D ideal magnetohydrodynamic simulation to study the propagation of CMEs traveling with different speeds in the heliospheric equatorial plane. The simulation confirms the existence of the CME deflection in the interplanetary space, which is related to the difference between the CME speed (v(r)) and the solar wind speed (v(sw)): a CME will propagate radially as v(r) is close to v(sw) but eastward or westward when v(r) is larger or smaller than v(sw); the greater the difference is, the larger the deflection angle will be. This result supports the model for CME deflection in the interplanetary space (DIPS) proposed by Wang et al., predicting that an isolated CME can be deflected due to the pileup of solar wind plasma ahead of or behind the CME. Furthermore, the deflection angles, which are derived by inputting v(r) and v(sw) from the simulation into the DIPS model, are found to be consistent with those in the simulation.