Evolution of a coronal mass ejection from the Sun to Saturn

The prediction of the magnetic structure, arrival time, and arrival speed of coronal mass ejections (CMEs) at different locations in the heliosphere is a subject of intense study and great importance for understanding how CMEs evolve after they erupt. The magnetic structure of CMEs at the time of their eruption can be inferred through indirect proxies based on remote-sensing observations of the CME source region. However, the knowledge of the magnetic structure of CMEs at the Sun does not always imply a successful prediction of the magnetic structure at Earth, or in general in interplanetary space. This is because CMEs can change their orientation and shape due to deflections, rotations, and/or deformations. We present a case study of a filament eruption and related CME that took place in May 2012, aiming at estimating how the knowledge of the CME magnetic structure at the Sun can be used in the case of CMEs that are associated with rotating filaments. We aim at comparing the magnetic structure of the CME at the Sun with observations from multiple vantage points through the heliosphere, in order to describe how the CME evolves as it travels away from the Sun. We use remote-sensing observations of the solar disc, the corona, and the inner heliosphere, and in situ measurements taken at Venus, at Earth, at Mars, and at Saturn.