The life of a CME and the development of a MIR: From the Sun to 58 AU

Large coronal mass ejections (CMEs) have major effects on the structure of the solar wind in the heliosphere. The plasma and magnetic field can be compressed ahead of CMEs to form merged interaction regions (MIRs). One signature of some CMEs that can be used to track them through the heliosphere is an enhanced alpha abundance. We use this signature and a one‐dimensional MHD model to track a CME from an active region on the Sun to Wind (1 AU), then to Ulysses (5.3 AU) and finally to Voyager 2 (58 AU). The arrival times of the CME ejecta at the three spacecraft are identified primarily by the increased alpha abundance. The observed plasma profiles and timing are close to those predicted by propagating data outward (from Earth to Ulysses and from Ulysses to Voyager 2) using the MHD model and give us confidence we are observing the same events at all three spacecraft. This event and a subsequent CME bracket a developing MIR and thus allow us to track the development of this structure.