Our aim is to improve the understanding of the physical conditions in cool solar chromospheric and coronal structures which may lie below the current spatial resolution of our telescopes. The model used solves the radiative transfer and statistical equilibrium equations in a two-dimensional cross-section of a cylindrical structure. The cylinder is filled with a mixture of hydrogen and helium, and is illuminated at a given altitude from the solar disc. The calculations are used to produce synthetic emergent spectra from loop structures.
We consider the effect of multiple loop structures within a given field of view and the effect of peculiar velocities between the structures in a multiple loop model. These new models are compared to the single loop model and tested with varying loop parameters.
We find that when assuming randomly displaced loops in a given field of view, the cross-sectional intensities of optical thick and thin transitions are considerably different. In optically thin lines the emergent intensity increases proportionally with the number of loops and the cross-section becomes increasingly homogeneous. Optically thick lines however saturate after only a few loops, and retain much cross-sectional structure. The multiple loop model creates asymmetric and more complex line profiles if line-of-sight velocities are added for each loop. Assuming the velocities are randomly generated, the line profiles exhibit significant asymmetries after a small number of loops.