Bayesian Estimation and Breathing Modes of the Heliosheath Distance from IBEX Data

The Interstellar Boundary Explorer (IBEX) has measured energetic neutral atoms (ENAs) originating from charge-exchange with outgoing solar wind particles in the outer heliosphere since the spacecraft's launch in 2008. In 2021, Reisenfeld et al. analyzed a solar cycle of IBEX data, estimating the distance to and thickness of the heliosheath, which is believed to be the principal source of ENAs observed by IBEX. Their paper considered the ENA flux in 56 macro-pixels covering the full sky, and the analysis forward-modeled equations for ENA propagation times to determine distances based on optimal cross-correlations. We present a follow-up analysis of this data set, using Bayesian inference to derive posterior probability distributions for every macro-pixel. This method provides a framework to incorporate physics-informed uncertainty quantification of the heliosheath distance. Further analysis investigates the temporal variability in each direction. Frequentist Fourier-spectral analysis is used to estimate the heliosheath's sensitivity to solar wind variability, developing techniques to study putative breathing modes. This work is presented in its theoretical context and with prospects for application to the Interstellar Mapping and Acceleration Probe (IMAP), set to launch in 2025.