The upper boundary condition for an atmosphere is determined by heliophysical processes responding to incident stellar drivers, the planet’s induced or intrinsic magnetic field, and the composition and characteristics of the atmosphere itself. Understanding the fundamental physics at work benefits from study of all accessible upper atmosphere systems, using a broad array of computational and experimental techniques. Venus is a particularly relevant laboratory for such study, given its unique combination of Earth-like mass, Mars-like upper atmosphere composition, inferred history of volatile loss, exposure to harsher solar input than Earth, and its near-total absence of planetary rotation, obliquity, and intrinsic magnetic fields. We welcome contributions about the heliophysics governing atmospheric escape and its consequences for the retention of habitable atmospheres, from modelers, theoreticians, and observers, particularly those studying Venus and Venus-like exoplanets, but also from those studying Earth, other solar system bodies, and exoplanets and their host star environments.

• SA - SPA-Aeronomy
• SH - SPA-Solar and Heliospheric Physics
• SM - SPA-Magnetospheric Physics