The solar abundance of beryllium : constraining the solar problem via non-LTE modelling

Sammanfattning: Accurately determining the solar abundance of beryllium is a key to calibrate transport processes at the base of convective zone, which in turn is an improvement upon existing solar models and general understanding of the physical processes within the Sun. To determine an abundance, assumptions about the solar atmosphere must be made. While it is common to assume local thermodynamic equilibrium (LTE) due to the simplicity this brings to the calculations, it is more accurate to assume non-local thermodynamic equilibrium (non-LTE), because it better resembles the physics of the solar atmosphere, where observed spectral lines form. Non-LTE calculations require a model atom that will provide important information about the atom to the radiative transfer code in order to preform necessary calculations. In this project, the solar abundance of beryllium was studied with main purpose of calculating the non-LTE abundance correction to be applied on already known LTE abundances. This was done by creating a comprehensive model atom of beryllium, containing essential information about the atom’s states as well as radiative and collisional transitions coupling those states. Simulations using radiative transfer code were performed and their results analysed to compute non-LTE abundance correction for the solar 3D LTE abundance A(Be) = 1.38. Resulting correction was computed to be equal to +0.03, which, when applied on the LTE abundance,does not affect the abundance significantly, contrary to the -0.060 correction of Korotin &Kučinskas (2021). A possible reason for this result might be that the model atom includes additional collisional transitions (Kaulakys collisions), omitted in Korotin+.