The impact of the transport of chemicals and electronic screening on helioseismic and neutrino observations in solar models

TL;DR

This paper investigates how chemical transport processes and electronic screening affect helioseismic and neutrino observations in solar models, comparing different diffusion formalisms and including additional mixing processes to match observational constraints.

Contribution

It provides a detailed comparison of atomic diffusion formalisms in solar models and assesses the impact of extra mixing and electronic screening on helioseismic and neutrino data.

Findings

Different diffusion formalisms produce varying helioseismic constraints.

Extra mixing processes are necessary to reproduce light element depletion.

Electronic screening significantly influences neutrino flux predictions.

Abstract

The transport of chemical elements in stellar interiors is one of the greatest sources of uncertainties of solar and stellar modelling. The Sun, with its exquisite spectroscopic, helioseismic and neutrino observations, offers a prime environment to test the prescriptions used for both microscopic and macroscopic transport processes. We study in detail the impact of various formalisms for atomic diffusion on helioseismic constraints in both CLES (Scuflaire et al., 2008a) and Cesam2k2 (Morel and Lebreton 2008; Marques et al. 2013; Deal et al. 2018) models and compare both codes in detail. Moreover, due to the inability of standard models using microscopic diffusion to reproduce light element depletion in the Sun (Li, Be), another efficient process must be included to reproduce these constraints (rotation-induced: Eggenberger et al. 2022, overshooting -- or penetrative convection -- below the convective envelope: Th\'evenin et al. 2017, or ad hoc turbulence: Lebreton and Maeder 1987; Richer, Michaud, and Turcotte 2000). However, introducing such an extra mixing leads to issues with the CNO neutrino fluxes (see Buldgen et al. 2023), which seem to be systematically lower than the Borexino observations (Appel et al., 2022. Another key aspect to consider when reconciling models with neutrino fluxes is the impact of electronic screening (Mussack and D\"appen, 2011).