ON FAST MAGNETOSONIC CORONAL PULSATIONS

The linear properties of the fast magnetosonic modes of a coronal loop modelled as a smooth density inhomogeneity in a uniform magnetic field are compared with the case of a step function slab. It is shown that the group velocity C-g of the modes, important in determining the structure of impulsively excited wave packets, possesses a minimum for a wide class of profile including the slab, with the exception of the Epstein profile for which the minimum in C-g moves out to infinity. Results for the simple step profile are thus of wider validity, and likely to be applicable to coronal loops.