Identical Interplanetary Coronal Mass Ejection Signatures with Wide Angular Separation

On March 12, 2012, a Coronal Mass Ejection (CME) was released from the Sun with a speed of ~2000 km/s. The CME source region was surrounded by three different coronal holes (CHs), located to the East (negative polarity), South-West (positive polarity) and West (positive polarity). Its interplanetary counterpart (ICME) impacted Earth and was in-situ measured by the Advanced Composition Explorer (ACE) / Wind at L1 and the Solar TErrestrial RElations Observatory Ahead (STEREO)-A on March 15th. During this period, the angular separation between the two locations was greater than 100 degrees. Nevertheless, the in-situ measurements revealed almost identical profiles with clear markers of ICME signatures, which is evidence of one of the widest reported multi-spacecraft detection of an ICME, having STEREO-A crossing the west flank and Earth the east flank. Supra-thermal electrons show signatures of bidirectionality and isotropy/simple strahl as  the ICME crosses the different spacecraft, providing information about the eroded parts of the ICME. Certain parts might have been  eroded, possibly due to the interaction with the fast solar wind produced by the nearby CHs. We analysed the propagation of the ICME structure using remote-sensing observations from both STEREOs and Earth together with different in-situ instrumentation at ~1 au, and performed a comparison between the physical properties derived at multiple spacecraft. This study shows the importance of multi-spacecraft observations to understand the large-scale structures of ICMEs, their evolution and interaction, as well as their implications for the space-weather discipline.