EVOLUTION OF A MAGNETIC-FLUX TUBE IN A SUNSPOT PENUMBRA

The motion of an individual magnetic flux tube inside the penumbra of a sunspot is studied numerically, Here, we present preliminary results . The thin flux tube approximation together with a simplified radiativ e heat exchange with the surroundings is used to study the evolution o f a flux tube embedded into a background given by a global magneto-sta tic sunspot model, The investigation is undertaken in order to verify the conjecture that convection in sunspot penumbrae occurs by an inter change of magnetic flux tubes. The code being developed can be used to study dynamic aspects of filamentary structure in the penumbra: the t emporal and spatial fluctuations of the temperature and the magnetic f ield, the motion of bright penumbral grains, or the Evershed effect, H ere we present the evolution of a wave formed by the tube whose fragme nt emerges in the penumbral photosphere and migrates towards the umbra . The properties of this wave show qualitative features of the observe d bright penumbral grains with corresponding upward velocity and its c orrelation with brightness and the inclination of the magnetic field, and also of the Evershed effect.