The Magnetic Morphology of Magnetic Clouds: Multi-spacecraft Investigation of Twisted and Writhed Coronal Mass Ejections

We present a study about the structure of the magnetic field inside coronal mass ejections (CMEs) with consideration of the helicity property of the magnetic field lines. We perform reconstructions and fittings of the magnetic field of two simulated CMEs: (1) a CME with writhed magnetic field lines and minimum twist, and (2) a CME with a twisted flux rope structure. Our aim is to gain insight into the structure of the CMEs’ magnetic field through comparing the outcome of the fitting techniques with the actual structure of the simulated CMEs. Reconstructions are performed at 12 different locations using the Grad–Shafranov reconstruction technique and a force-free fitting technique. These locations correspond to different impact parameters, as well as different longitudinal planes in the CME “legs.” We find that a flux rope CME and a writhed CME cannot be distinguished by comparing the best-fit orientation at different locations. We also find that the reconstructed shapes and impact parameters may provide some clues about the presence of substantial writhe. Because of the difficulty for present codes to detect writhe, we conclude that reconstruction codes and fitting techniques have to be significantly improved, by taking into consideration the writhe of the magnetic field lines.status: publishe