Authors: Nada Al-Haddad (UNH) & Noé Lugaz (UNH)

Coronal Mass Ejections (CMEs) are highly dynamic and complex structures, which are central for solar-terrestrial science. However,  their magnetic field structures are often oversimplified in standard models. While CMEs have traditionally been described as highly twisted flux ropes with circular cross-sections, both remote and in situ observations over the past several decades show that most events do not fit this picture.

We present here a comprehensive review on how observational and modeling results point to a more complex reality: CMEs frequently have elliptical or distorted cross-sections, weakly twisted and complex magnetic twist, and a combination of open and closed field lines. Multi-spacecraft measurements and reconstruction techniques reveal that CME axes are often kinked or non-existent, and their overall structure is distinctly three-dimensional.

We suggest an updated paradigm and visual representation to reflect these findings in order to improve our understanding of the structure CMEs and their potential impacts in the heliosphere.