Global Heliospheric Termination Shock Strength in the Solar-Interstellar Interaction

A heliospheric termination shock (HTS) surrounds our solar system at approximately 100 astronomical units from the Sun, where the expanding solar wind (SW) is compressed and heated before encountering the interstellar medium. HTS-accelerated particles govern the pressure balance with the interstellar medium, but little is known about the HTS's global properties beyond in situ measurements from Voyager in only two directions of the sky. We fill this gap in knowledge with a novel and complex methodology: particle-in-cell, test particle, and MHD simulations, combined with a global minimization scheme to derive global HTS compression ratio sky maps. The methods utilize Interstellar Boundary Explorer observations of energetic neutral atoms produced from HTS-accelerated particles. Our results reveal unique, three-dimensional characteristics, such as higher compression near the poles during solar minimum, north-south asymmetries from the disparate polar coronal holes' evolution, and minimum compression near the flanks likely from SW slowing by mass-loading over a greater distance to the HTS.