9–13 Mar 2015
Albanova, Stockholm
Europe/Stockholm timezone

Flux emergence: simulations and observations

10 Mar 2015, 10:50
40m
Oskar Klein Auditorium (Albanova, Stockholm)

Oskar Klein Auditorium

Albanova, Stockholm

Speaker

Bob Stein (Michigan State University)

Description

Simulation results will be shown for two cases: weak, non-buoyant and strong, buoyant uniform, untwisted, horizontal magnetic fields advected into the computational domain by inflows at 20 Mm depth. Convection both shreds the magnetic field into many thin fibrils as well as keeps the larger-scale structure confined within the inflow supergranule cell. Convective upflows and downflows bend the field into serpentine loops. Magnetic field first emerges as horizontal field over granules with vertical legs in the intergranular lanes and elongates the granules in the field direction. Because of the fibril substructure, the field first emerges in a mixed polarity, "pepper and salt" pattern. As the underlying, large-scale loop emerges, the opposite polarity components at the surface stream into uni-polar flux concentrations at its nearly vertical legs. The three most obvious differences between the weak and strong field cases are: first, the buoyant loop emerges much more quickly (1 day vs 2 days from 20 Mm); second, the weak field does not distort the supergranule-scale convective cells while the strong field enlarges the cells in the field direction which results in the opposity polarit legs spreading apart; third, the field is more horizontal surrounding the leg remaining behind in the strong field case.

Primary author

Bob Stein (Michigan State University)

Co-author

Aake Nordlund

Presentation materials