On the Stability of Small-Scale Magnetic Elements in the Quiet Photospheric Network

Abstract

28 min time series of high resolution magnetograms, continuum filtergrams and line core filtergrams have been obtained in the line FeI 6173 Å with the 50 cm refractor of the Pic du Midi Observatory, in a quiet area near the solar disk center. Their comparison shows that every bright point of the photospheric network is associated with a magnetic element of small size (smaller than 1″); their locations do not coincide exactly, but are however within less than 0.5″. The maximum of magnetogram signal of a magnetic element does not necessarily occur at the same time as the maximum of the brightness. Such spatial and temporal relations cannot be explained by static models of flux tubes, but they can be by a dynamic flux tube model, as computed recently by Steiner and al. (1996). The observations also show that a magnetic element present in the network becomes bright and forms a bright point, when it is compressed by the surrounding granules as they converge. This is an indication that the dynamics of granulation play a major role in the concentration of the magnetic field into thin flux tubes, near the surface of the Sun.