Transfer in cylindrical fluxtubes, with 1or 2 dimensions

Abstract

This is a review of methods for the solution of non-LTE radiativetransfer equations in long cylinders. The principal goal of thesemethods is the modelling of elongated structuresimbedded in the solar corona, such as loops or prominence threads.These objects are submitted to the solar radiation, which determinesthe boundary conditions of the problem. Different cases areexamined. Concerning the geometry, one-dimension and two-dimensioncases are treated. The two-dimension case itself is subdivided into(radius, altitude) and (radius, azimuth) problems, which are treated byquite different methods. Another distinction concerns the method ofresolution: semi-analytical, Monte-Carlo and finite-differencemethods are examined. Some methods are restricted to a two-levelatom, others allow the treatment of realistic multilevel cases. Somerecent results, obtained with finite-difference, acceleratedΛ-iteration methods, are presented.