Toward Explaining Galactic Cosmic-Ray Modulation in a Dynamic Heliosheath: Transient Structures Seem Dominant and Magnetic Drifts Appear Reduced

Abstract While traveling through the heliosheath (HS), Voyager 2 observed sustained flux depletions of galactic cosmic rays (GCRs) on scales of months to years. In this work, we shed light on these measurements through test particle simulations in a time-dependent, analytic model of the heliosphere using the SPECTRUM software. This work concludes that high-energy cosmic-ray modulation in the HS is a highly dynamic process, and space weather effects are still relevant in the outer heliosphere. GCR transport appears to be dominated by large, transient modulation structures advected from the Sun, while the role of spatially dictated diffusion is likely secondary. Additionally, our results suggest that the strength of magnetic drifts in the HS is lower than the classical (weak-scattering limit) formulas predict.