The modes of oscillation of a prominence. III. The slab in a skewed magnetic field.

Abstract

We consider theoretically the possible modes of oscillation of a solar quiescent prominence, treating the prominence as a plasma slab embedded in a uniform, line-tied magnetic field that is inclined at a small angle (≃ 20°) to the long axis of the slab. Particularly interesting is the appearance of a string Alfven mode that is analogous to the fundamental mode of vibration of a stretched string loaded with a heavy mass at its centre. This mode, along with a slow internal mode of the slab, may correspond to the observed long period (40-90 min) oscillation of quiescent prominences. Intermediate periodicities, in the range 8-20 min, may be associated with an internal Alfven mode and a fast string mode