Radiative transfer in cylindrical threads with incident radiation

A numerical code is proposed for the solution of NLTE radiative transfer equations in long cylinders, including multilevel atoms and anisotropic incident radiation (which implies a 2-dimension treatment of the radiation field). It is applied to the modelling of the hydrogen spectrum emitted by magnetic loops imbedded in the solar corona. The model hydrogen atom includes 10 levels and one continuum. The intensities emitted by loops in the most important hydrogen lines and in the Lyman continuum are discussed using a set of isothermal and isobaric models. The case of loops with a radial temperature gradient is also investigated.