Fast MHD oscillations in prominence fine structures

Abstract

High-resolution observations suggest that quiescent solar prominences are made of small-scale brils stacked one after another in both the vertical and horizontal directions. These brils are interpreted as the cool, highermost part of much larger coronal loops which are rooted in the solar photosphere. On the other hand, there is some evidence showing that small amplitude oscillations in prominences can aect individual or groups of brils, which vibrate with their own periods. Using a simple magnetostatic model to represent the bril structure of quiescent solar prominences, Joarder et al. (1997) investigated some oscillatory properties of the Alfv en and fast magnetohydrodynamic modes. In this paper, with a proper treatment of boundary conditions, we reexamine their conguration 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 bril's width, perturbations extend far away from its axis and, therefore, a single oscillating bril can excite oscillations in neighbouring ones.