Unveiling the Journey of a Highly Inclined CME: Insights from the March 13, 2012 Event with 110^∘ Longitudinal Separation

A fast and wide Coronal Mass Ejection (CME) erupted from the Sun on2012-03-13. Its interplanetary counterpart was detected in situ two days laterby STEREO-A and near-Earth spacecraft. We suggest that at 1 au the CME extendedat least 110^∘ in longitude, with Earth crossing its east flank andSTEREO-A crossing its west flank. Despite their separation, measurements fromboth positions showed very similar in situ CME signatures. The solar sourceregion where the CME erupted was surrounded by three coronal holes (CHs). Theirlocations with respect to the CME launch site were east (negative polarity),southwest (positive polarity) and west (positive polarity). The solar magneticfield polarity of the area covered by each CH matches that observed at 1 au insitu. Suprathermal electrons at each location showed mixed signatures with onlysome intervals presenting clear counterstreaming flows as the CME transits bothlocations. The strahl population coming from the shortest magnetic connectionof the structure to the Sun showed more intensity. The study presents importantfindings regarding the in situ measured CME on 2012-03-15, detected at alongitudinal separation of 110^∘ in the ecliptic plane despite itsinitial inclination being around 45^∘ when erupted. This suggests thatthe CME may have deformed and/or rotated, allowing it to be observed near itslegs with spacecraft at a separation angle greater than 100^∘. The CMEstructure interacted with high-speed streams generated by the surrounding CHs.The piled-up plasma in the sheath region exhibited an unexpected correlation inmagnetic field strength despite the large separation in longitude. In situobservations reveal that at both locations there was a flank encounter, wherethe spacecraft crossed the first part of the CME, then encountered ambientsolar wind, and finally passed near the legs of the structure.