Deriving the interaction point of an Interplanetary Coronal Mass Ejection and High-Speed stream : A case study

Understanding the propagation and evolution of Coronal Mass Ejections (CMEs) is one of the fundamental problems in Heliospheric Physics. An important factor in comprehending the evolution of CMEs in interplanetary space (ICMEs) is studying the different interactions they undergo, such as with high-speed streams (HSS) originating from coronal holes (CH). We study the interaction of an ICME detected in situ at the L1 Lagrange point on 12th October 2016 with a trailing HSS. The in-situ measurements indicate a Magnetic Obstacle (MO) with a symmetric flux rope structure and reconnection exhaust signatures at the ICME-HSS boundary. The ICME is associated with a Halo CME recorded in the LASCO CME catalogue on 9th October 2016. We use Graduated Cylindrical Shell (GCS) reconstruction to obtain 3D CME characteristics and SDO AIA 193 Å measurements to analyse basic CH properties. We next use "a two-step Drag Based Model (DBM)" together with EUropean Heliospheric FORecasting Information Asset (EUHFORIA) to model and analyse the interaction and estimate where in the heliosphere the interaction takes place. We find that the results from the two-step DBM model give better justification for the observed in-situ signatures compared to the EUHFORIA run; this could be due to the lack of reliable magnetogram data from the backside of the Sun. Our analysis indicates that the interaction between ICME and HSS initiated relatively close to Earth (~0.9 AU), providing a benchmark to study ICME-HSS interaction at an early phase.