Galactic Gas Models Strongly Affect the Determination of the Diffusive Halo Height

TL;DR

This paper demonstrates that the modeling of the Milky Way's spiral arms significantly influences the constraints on the cosmic-ray diffusive halo height derived from radioactive secondary flux measurements.

Contribution

It introduces advanced spiral arm models to improve predictions of radioactive secondary fluxes, highlighting the impact of galactic structure on halo height estimates.

Findings

Spiral arm modeling biases halo height constraints.

New flux predictions for AMS-02 and HELIX.

Galactic structure critically affects cosmic-ray measurements.

Abstract

The height of the Milky Way diffusion halo, above which cosmic-rays can freely escape the galaxy, is among the most critical, yet poorly known, parameters in cosmic-ray physics. Measurements of radioactive secondaries, such as $^{10}$Be or $^{26}$Al, which decay equivalently throughout the diffusive volume, are expected to provide the strongest constraints. This has motivated significant observational work to constrain their isotopic ratios, along with theoretical work to constrain the cross-section uncertainties that are thought to dominate radioactive secondary fluxes. In this work, we show that the imprecise modelling of the Milky Way spiral arms significantly affects our ability to translate $^{10}$Be and $^{26}$Al fluxes into constraints on the diffusive halo height, biasing our current results. Utilizing state-of-the-art spiral arms models we produce new predictions for the $^{10}$Be and $^{26}$Al fluxes that motivate upcoming measurements by AMS-02 and HELIX.