The Structural Connection between CME Flux Ropes near the Sun and at 1 AU

We preformed the first comprehensive statistical analysis comparing flux rope structures of coronal mass ejections (CMEs) near the Sun and at 1 AU, using SOHO and STEREO measurements for the two full solar cycles of 23 and 24. The study aims to investigate the physical connection of 102 magnetic flux ropes (FR) among solar source regions, CMEs in the extended corona, and magnetic clouds (MCs) near Earth. Our main results include: 1) We confirmed that the hemispheric helicity rule holds true for $\sim$ 87\% of our 102 events. For the thirteen events that do not follow this rule, the FR axis directions and helicity signs can be inferred from soft X-ray and EUV images and magnetogram data in the source regions (e.g., coronal arcade skews, sigmoids, and magnetic tongues). 2) Around 25\% of the 102 events have rotations $>$ 40\dg between the MC and CME--FR axial orientations. 3) For $\sim$56\% of these rotational events, the flux rope rotations occurred within the COR2 FOV, which can be predicted from the CME tilts obtained from flux rope fitting models. In addition, we found that for 89\% of the nineteen stealth CMEs under study, we can use the CNL locations and tilts to predict the flux rope helicity and its axial direction in the MCs. The above results would help to improve the prediction of the flux rope structures in situ. We discuss their implications on space weather forecasts.