Authors: Nehpreet K. Walia (Princeton University) , Daniel B. Reisenfeld (Los Alamos National Laboratory), David J. McComas (Princeton University), Herbert O. Funsten (Los Alamos National Laboratory), Sung Jun Noh (New Mexico Consortium, Los Alamos National Laboratory) , Eric J. Zirnstein (Princeton University, University of Alabama), Lengying Khoo (Princeton University), Manuel E. Cuesta (Princeton University), Fan Guo (Los Alamos National Laboratory), Richa N. Jain (Princeton University), Paul H. Janzen (University of Montana), Thomas K. Kim (Los Alamos National Laboratory), George Livadiotis (Princeton University), Jamie S. Rankin (Princeton University), Mitchell M. Shen (Princeton University), Jeongbhin Seo (Los Alamos National Laboratory), Bishwas L. Shrestha (Princeton University) and Jamey R. Szalay (Princeton University)

When multiple Coronal Mass Ejections (CMEs) occur within a relatively short time interval, they can merge with each other, forming merged interaction regions (MIRs). The impact of these transient MIR events in the solar wind (SW) can be observed at large distances from the Sun throughout our heliosphere [e.g., Richardson et al., 2022]. The heliosheath is a source of a broad distribution of energetic neutral atom (ENA) flux that varies across the sky, and we can detect it using NASA’s Interstellar Boundary Explorer (IBEX). A major finding from IBEX is that this flux is remarkably dynamic, responding to changes in the solar wind on short time scales (< 6 months), a finding originally unexpected considering the enormous size of the heliosheath [McComas et al., 2024]. Although large changes in the global state of the SW have been detected in ENA maps [e.g, McComas et al., 2018, Walia et al., 2025], a conclusive macroscopic signature of a SW transient has yet to be reported in ENA maps. We report here the direct large-scale detection of a SW transient event in IBEX data and the resulting changes in the heliosheath energetics.