Stability of a flux tube model for prominences

We discuss the stability of a flux tube model for quiescent solar prominenc es. The main result is that the configurations are stable only up to a crit ical width (defined as the extension of the central part of the flux tube w ith prominence matter at low temperatures) of about 1 000 km to 3 000 km. T he dependence of the critical width on the prominence parameters height, te mperature, density contrast, external magnetic field, external gas pressure and external temperature is analysed. The normal modes and eigenfrequencie s obtained numerically cover the range of observational data for prominence oscillations.