Through the Heliospheric Lens: Directional Deflection of High-Energy Cosmic-Ray Electrons and Positrons

Abstract

We investigate how the large-scale heliosphere alters the arrival directions of high-energy cosmic-ray electrons and positrons and ask if and when this "heliospheric lens" can be ignored for anisotropy and source-association studies - an especially timely topic given, for instance, the persistent cosmic-ray positron fraction and its unknown origin. Using a modular back-tracing framework, we explore a set of widely used magnetic-field descriptions-from a Parker spiral baseline to more structured configurations that include latitudinal wind contrasts, Smith-Bieber-type azimuthal strengthening, and tilted or wavy heliospheric current sheets. We model the deterministic deflections of high-energy cosmic-ray electrons and positrons (CREs) induced by large-scale heliospheric magnetic-field structures using a back-tracing approach. Our results apply to CREs above tens of GeV, where diffusion, convection, and adiabatic energy losses play a subdominant role; these processes are neglected in the present study and will be addressed in future work. Across these models the picture is consistent: most bending is accumulated within the inner tens of astronomical units and decreases rapidly with energy. Field choices and solar-cycle geometry set the overall normalization, with stronger spiral winding or a more highly tilted current sheet producing larger deflections at the same energy. Differences between electrons and positrons are most apparent at lower energies, where drift histories and current-sheet encounters diverge, and become increasingly small at multi-TeV energies. [...]

Comments: 22 pages, 9 figures; v2: 25 pages, same 9 figures, accepted for publication