Aims. Magnetic elements are thought to be described by flux tube models, and are well reproduced by MHD simulations. However, these simulations are only partially constrained by observations. We observationally investigate the relationship between G-band bright points and magnetic structures to clarify conditions, which make magnetic structures bright in G-band. Methods. The G-band filtergrams together with magnetograms and dopplergrams were taken for a plage region covered by abnormal granules as well as ubiquitous G-band bright points, using the Swedish 1-m Solar Telescope (SST) under very good seeing conditions. Results. High magnetic flux density regions are not necessarily associated with G-band bright points. We refer to the observed extended areas with high magnetic flux density as magnetic islands to separate them from magnetic elements. We discover that Gband bright points tend to be located near the boundary of such magnetic islands. The concentration of G-band bright points decreases with inward distance from the boundary of the magnetic islands. Moreover, G-band bright points are preferentially located where magnetic flux density is higher, given the same distance from the boundary. There are some bright points located far inside the magnetic islands. Such bright points have higher minimum magnetic flux density at the larger inward distance from the boundary. Convective velocity is apparently reduced for such high magnetic flux density regions regardless of whether they are populated by G-band bright points or not. The magnetic islands are surrounded by downflows. Conclusions. These results suggest that high magnetic flux density, as well as efficient heat transport from the sides or beneath, are required to make magnetic elements bright in G-band.Key words. Sun: magnetic fields -Sun: faculae, plages -convection IntroductionMagnetic fields on the Sun have various spatial and time scales. Sunspots have the largest scale size (∼10 4−5 km) with long lifetimes (∼1 month) and very high contrast, while magnetic elements often observed in the Fraunhofer G-band (the CN band, the wing of Ca H and K, and continuum) are the smallest resolved structures, and are believed to be building blocks of active regions and the quiet Sun magnetic network. In the 1970s, filigree structures in the intergranular lanes and faculae observed at the solar limb were reported (Dunn & Zirker 1973;Mehltretter 1974), and these small bright points were believed to be a manifestation of elemental magnetic fields (Spruit 1976(Spruit , 1977. Beckers & Schröter (1968) originally observed small magnetic features called magnetic knots with magnetic field strength between 1000−2000 G. Recent high-resolution observations have been able to resolve these magnetic knots into smaller magnetic elements. The question of how such small structures with strong magnetic flux density and with short lifetime exist is one of the central issues in solar magnetohydrodynamics. Direct magnetic observations of the magnetic elements are, however, diffic...

Proper motions in a sunspot group with a delta-configuration and close to the solar disc center have been studied by employing local correlation tracking techniques. The analysis is based on more than one hour time series of G-band images. Radial outflows with a mean speed of 0.67 km s^{-1} have been detected around the spots, the well-known sunspots moats. However, these outflows are not found in those umbral core sides without penumbra. Moreover, moat flows are only found in those sides of penumbrae located in the direction marked by the penumbral filaments. Penumbral sides perpendicular to them show no moat flow. These results strongly suggest a relation between the moat flow and the well-known, filament aligned, Evershed flow. The standard picture of a moat flow originated from a blocking of the upward propagation of heat is commented in some detail.Comment: 4 pages, 4 figures, To appear in ApJ Letter