Warmer Local Interstellar Medium: Resolving the Ulysses-Ibex Enigma and the Promise of IMAP

While charged particles from the local interstellar medium (LISM) are convected around our heliosphere with the magnetized LISM flow, the neutral interstellar atoms flow directly into and through the heliosphere. Initial measurements from the Interstellar Boundary Explorer (IBEX) suggested that the heliosphere could be moving more slowly with respect to the interstellar medium than indicated by earlier observations from the Ulysses spacecraft. In this study we refine the range of possible IBEX flow parameters based on the latest measurements and show that both spacecraft’s data could be consistent with a single flow velocity for a much larger interstellar neutral temperature (7000-9000K) than previously found. Combining the IBEX and Ulysses observations suggests that the heliosphere is currently in a substantially warmer region of the interstellar medium than previously thought. This study examines this possible resolution of the prior apparent disconnect between these observations. We further examine the incredible improvement in interstellar observations – and our understanding of the local interstellar medium – that the envisioned Interstellar Mapping and Acceleration Probe (IMAP) will provide.