APEC Seminar (Astronomy - Particle Physics - Experimental Physics - Cosmology)

Speaker: Antonio Ferriz (IAA/CSIC Granada and Universidad de Vigo, Spain)
Date (JST): Thu, Apr 06, 2017, 13:30 - 14:30
Place: Seminar Room A
Abstract: The existence of a hierarchy of concentrated magnetic structures in the observable layers of the Sun is indicative of the intermittent nature of magnetic fields in the underlying convection zone and this should also be the case for solar-like stars. The study of the structure and dynamics of magnetic fields in stars is a complex mathemat-ical problem due to the nonlinear nature of the magnetohydrodynamic (MHD) equations, to the presence of boundary layers and to the inhomogeneities involved. The filamentary nature of magnetic fields in the convection zone allows for a considerable simplification of the MHD equations. The thin flux-tube approximation permits the reduction of the full set of MHD equations to a mathematically more tractable form without making any restriction on the compressibility of the plasma, the magnetic Lorentz force or gravity. In physical terms, the approximation amounts to assuming that the variation of the physical properties over the cross section of the tube is small as compared with the variation along it (with the exception of a jump at the boundary). With the aid of the thin flux-tube approximation it is possible to obtain a consistent model of magnetic field storage, instability, dynamics and eruption.