Spectro-polarimetric simulations of the solar limb: absorption-emission FeI $6301.5\mathrm{\AA}$ and $6302.5\mathrm{\AA}$ line profiles and torsional flows in the intergranular magnetic flux concentrations

TL;DR

This study uses advanced simulations and spectro-polarimetric diagnostics to analyze the solar limb's radiation properties, revealing emission features linked to magnetic fields and torsional motions in intergranular flux concentrations.

Contribution

It introduces detailed modeling of solar limb line profiles, highlighting the role of magnetic fields and torsional flows in emission features, which was not previously well understood.

Findings

Profiles with emission and absorption features at the limb.

Pure emission profiles observed above the limb.

Emission wings caused by local heating and torsional motions.

Abstract

Using radiative magneto-hydrodynamic simulations of the magnetised solar photosphere and detailed spectro-polarimetric diagnostics with the FeI $6301.5\mathrm{\AA}$ and $6302.5\mathrm{\AA}$ photospheric lines in the local thermodynamic equilibrium approximation, we model active solar granulation as if it was observed at the solar limb. We analyse general properties of the radiation across the solar limb, such as the continuum and the line core limb darkening and the granulation contrast. We demonstrate the presence of profiles with both emission and absorption features at the simulated solar limb, and pure emission profiles above the limb. These profiles are associated with the regions of strong linear polarisation of the emergent radiation, indicating the influence of the intergranular magnetic fields on the line formation. We analyse physical origins of the emission wings in the Stokes profiles at the limb, and demonstrate that these features are produced by localised heating and torsional motions in the intergranular magnetic flux concentrations.