Non-Radial Propagation and Magnetic Field Evolution of Large-scale Magnetized Plasmoid from the Sun to Mars

The large-scale magnetized plasmoids erupted from the Sun, such as coronal mass ejections (CMEs), would significantly influence the space weather environment when they hit the Earth. But, whether CMEs propagated along a straight path or curved path (deflection) in the interplanetary space is still debated. This different opinion has a strong impact on the heliospheric physics and space weather forecast. Here, we present a study of a fast coronal CME initially directed toward Mars, synthesizing observations from five space missions and employing three complementary modeling approaches. Magnetic field fitting with the 3Dcore model indicates an eastward deflection of approximately 31+/- 5 in longitude during the CME's propagation from the Sun to Mars. Besides the deflection, in situ magnetic field observations from ESA's BepiColombo, CNSA's Tianwen-1, and NASA's MAVEN missions further reveal pronounced writhing and magnetic erosion of the CME flux rope during its interplanetary transit. These multi-point observational results provide compelling evidence of both deflection and internal evolution of large-scale magnetized plasmoids, offering new view of constraints on heliospheric propagation models and enhancing the reliability of future space weather forecasting.