Dynamics of MHD perturbations in the presence of singular lines

Typical effects relevant to space and laboratory plasmas, induced by the presence of singular lines in a magnetic configuration, are presented. They refer to modifications of flute perturbations in the scrape-off layer of a divertor, the onset of stochasticity around the magnetic separatrix, and the trapping of fast MHD waves in the vicinity of singular lines. In particular, a WKB analysis performed for X-point and current sheet configurations points out the occurence of global modes characterized by regular and irregular trajectories.