Observations and models of solar active region loops

In the present work SOHO/CDS observations of a quiescent active region loop are compared to a steady-state, dynamic loop model, with three different heating functions. Predicted temperature and density profiles of the loop axe compared to observations from CDS. The space of parameters of the model is investigated. We find that no agreement can be found between model predictions and observations. We also analyze several SUMER intensity maps of active region solar loops in order to compare the observed relative brightnesses of their footpoints and of their coronal section, with predictions from loop models having uniform cross section and different heating functions. We find that the loop models overestimate the footpoint emission by orders of magnitude. We speculate that a significant decrease of the cross-section near the footpoints, is the most likely solution to the discrepancy.