Speaker
Description
Granulation is a fundamental manifestation of near-surface convection in cool main- sequence stars and plays a central role in regulating photospheric structure, spectral variability, and radiative output. Understanding its imprint on spectral lines is essential for connecting solar observations with unresolved stellar measurements and for improving models of stellar surface convection.
In this study, we analyse high-resolution MPS-ATLAS specific-intensity spectra emerging from the solar photosphere, simulated using the 3D radiative magnetohydrodynamic code MURaM, and investigate spectral line variability induced by granulation. We present a novel methodology based on the spatial variability of spectral line strengths and wavelength shifts and use it to examine the differential response of lines from neutral and singly ionised species to convective inhomogeneities.
We identify a clear and systematic distinction in the behaviour of these two groups. Temperature and velocity contrasts between granules and intergranular regions have a greater effect on the strengths of neutral lines and on the wavelength positions of singly ionised lines. This differential sensitivity provides new diagnostics of the thermodynamic and dynamic structure of granulation and establishes a framework for interpreting unresolved stellar spectra.