Fast MHD oscillations in prominence fine structures

High-resolution observations suggest that quiescent solar prominences are m ade of small-scale fibrils stacked one after another in both the vertical a nd horizontal directions. These fibrils are interpreted as the cool, higher most part of much larger coronal loops which are rooted in the solar photos phere. On the other hand, there is some evidence showing that small amplitu de oscillations in prominences can affect individual or groups of fibrils, which vibrate with their own periods. Using a simple magnetostatic model to represent the fibril structure of quiescent solar prominences, Joarder et al. (1997) investigated some oscillatory properties of the Alfven and fast magnetohydrodynamic modes. In this paper, with a proper treatment of bounda ry conditions, we reexamine their configuration and explore more deeply the basic features (mainly frequency and spatial structure) of the fast mode. The main conclusion is that, for reasonable values of the fibril's width, p erturbations extend far away from its axis and, therefore, a single oscilla ting fibril can excite oscillations in neighbouring ones.