Heliospheric Flow Separation and Vortex-Induced Interstellar Material Delivery: A Boundary Layer Analogy

Existing models of heliosphere-interstellar medium interaction treat the heliosphere as a passive shield subject to ram pressure compression during dense cloud encounters. This paper proposes an additional interaction regime applicable specifically at sharp interstellar medium density boundaries: flow separation analogous to aerofoil stall, producing vortex structures in the heliospheric wake that entrain and concentrate interstellar material, delivering it to the inner solar system through a mechanism distinct from simple compression. Where ram pressure compression delivers material uniformly as the heliosphere shrinks, vortex-induced entrainment delivers material in directionally asymmetric, rotationally structured packets from the wake side of the interaction. Geological evidence of interstellar material in terrestrial and lunar deposits — including ⁶⁰Fe and ²⁴⁴Pu isotopes — provides a testable substrate: if the vortex entrainment mechanism operates, the spatial distribution of these deposits should show directional asymmetry inconsistent with simple isotropic compression delivery. The hypothesis is conceptual; fluid dynamic modelling of the heliosphere under sharp density gradient boundary conditions is invited.