12 yr Full Solar Cycle Maps from IBEX-Lo Interstellar Neutral Atom Observations (2009–2020)

Abstract The Interstellar Boundary Explorer (IBEX) mission investigates the very local interstellar medium (VLISM) and its interaction with our heliosphere, partly by sampling interstellar neutral (ISN) atoms. Over 15 yr, IBEX has provided data to study this interaction through varying solar activity phases. Unlike ISN H, He interacts weakly with the heliospheric boundary and solar wind, offering a growing data set to enhance our knowledge of the VLISM and its motion relative to the Sun. We provide count rates and exposure time maps that capture ISN H and He as a function of orbit and spin angle for energy steps (E-Steps) 2 (29 eV) and 3 (55 eV) throughout solar cycle 24 (2009–2020). While E-Step 3 mainly captures ISN He, E-Step 2 rates include both ISN H and He. We show that these maps qualitatively agree with our model predictions. This data set, publicly available, provides an opportunity to study ISN flow and its response to solar activity. Our maps show variations of the primary ISN He intensity with solar activity; a remarkable decrease in the visibility of secondary He during solar maximum; the presence of ISN H signal in the rising phase of solar activity from 2009’s minimum, its disappearance during solar maximum, and reappearance toward cycle 25 minimum. This data set further demonstrates a potential ISN data configuration for the upcoming Interstellar Mapping and Acceleration Probe.