Ducted fast waves in coronal loops: curvature effects

We examine the effect of curvature on fast magnetoacoustic waves in dense coronal loops situated in a potential coronal arcade. The wave equation governing the velocity perturbations has been solved numerically under the zero-β approximation and in the absence of gravity. Due to the curvature of the structure, leaky waves arise. The extent of the leakage depends upon the length, width and density enhancement of the loop, as well as the frequency of oscillation and its geometrical nature. The sausage mode is more affected by curvature and is more leaky than the kink mode. An increase in length, width or gas density ratio reduces the leakage, whilst higher frequencies result in greater energy leakage. Odd modes of oscillation (zero velocity at the loop summit) are more strongly confined than even modes. Modes of oscillation may be destroyed by curvature and above a critical frequency ducted waves cease to exist.