Strong Interplanetary Evolution of Coronal Mass Ejection from BepiColombo at 0.67 AU up to Mars

The goal of this study is to understand the magnetic field evolution of an ICME event detected by pairs of aligned spacecraft at different heliocentric distances. In this work, we report a CME event that was detected by the BepiColombo spacecraft (0.67 AU) and Tianwen-1 & MAVEN (1.66 AU) in-situ measurements, respectively. We found that the dependence of the maximum (mean) magnetic field strength of the ICME at the two points decreases with heliocentric distance as r−1.07 (r−1.29). The axial magnetic field strength (B0) derived from the force-free flux rope model decreases with heliocentric distance as r−1.78, suggesting that the in-situ observations may show the CME may not expand in a self-similar manner due to the spacecraft crossing the flux rope in a different region. The axial magnetic flux and helicity of the magnetic cloud decreased approximately 13% and twist increased 17% from BepiColombo spacecraft to Mars, which implies that the CME event was eroded by the ambient solar wind. Utilizing the deflection in interplanetary space, we reconstruct the trajectory of the CME spanning from 21.5 Rs to 342 Rs under the constraints of the CME initial velocity and the simulated solar wind velocity. We present solid evidence that the fast CME event was deflected toward the east in the interplanetary, by approximately 16◦ at BepiColombo and 31◦ at Mars. The axis of the CME shows a clear clockwise rotation from 10.27◦ at BepiColombo to -12.45◦ at Mars.  The 3D coronal rope ejection model (3DCORE) model, the deflection in interplanetary space (DIPS) model and the reconstructed CME magnetic field structure and orientation from the Force-free flux rope fitting model were found to be in good agreement with each other. The analysis of this event highlights the inherent innovative potential in Tianwen-1’s magnetometer data, presenting a novel avenue for investigating magnetic clouds encircling Mars. Observations capturing the same magnetic cloud at various heliocentric distances present an unprecedented opportunity to scrutinize the cloud’s magnetic properties and their nuanced evolution relative to distance.