Convective blueshift inhibition from faculae to small network features

¹ Univ. Grenoble Alpes, CNRS, IPAG F-38000 Grenoble, France
² Université Aix Marseille, CNRS, CNES, LAM Marseille, France

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 11 April 2025
Accepted: 5 January 2026

Abstract

Context. Solar granulation properties have long been known to be affected by the presence of a magnetic field, which in turn affects the convective blueshift associated with magnetic regions. Their dependence on magnetic flux is, however, still poorly constrained.

Aims. We studied how the properties of the convective blueshift in faculae and network structures depends on their size and magnetic flux at different positions on the solar disc. We studied the velocity shifts at small (pixel) and intermediate (several granule) spatial scales. Finally, our aim was to validate that simple laws applied to complex structure configurations are sufficient to describe the observed disc-integrated radial velocities in a realistic way.

Methods. We analysed two series of HMI/SDO dopplergrams and magnetograms, which provide insights at different scales, to identify the Doppler shift associated with each structure and its properties. They were then used to evaluate their impact on radial velocity variability.

Results. We confirm the dominant role of the magnetic flux on the Doppler shift and dependence on distance from disc centre. However, we observe a saturation for large magnetic fluxes, as well as an unexpectedly large shift for the smallest network structures compared to that of the larger network structures. This may be due to the small-scale properties of the flows around the flux tubes or to the flux tube properties.

Conclusions. The quiet network strongly contributes to the long-term radial velocity variability, but also exhibits significant rotational modulation. Despite the diversity of properties from network to faculae, simple models to describe the convective blueshift are sufficient to capture the main properties of radial velocity variability in the solar case.