Radiative transfer in cylindrical threads with incident radiation: VII. Multi-thread models

Our aim is to improve on previous radiative transfer calculations in illuminated cylindrical threads to better understand the physical conditions in cool solar chromospheric and coronal structures commonly observed in hydrogen and helium lines. We solved the radiative transfer and statistical equilibrium equations in a two-dimensional cross-section of a cylindrical structure oriented horizontally and lying above the solar surface. The cylinder is filled with a mixture of hydrogen and helium and is illuminated at a given altitude from the solar disc. We constructed simple models made from a single thread or from an ensemble of several threads along the line of sight. We compared these new models to the single thread model and tested them with varying parameters. They can be used to interpret high-spatial and spectral resolutions of cylindrical structures found in the solar atmosphere, such as cool coronal loops or prominence threads.