On the Relation of G‐Band Bright Points to the Photospheric Magnetic Field

Abstract

Cotemporal observations in the 4305 A G-band and Ca II λ3933 K-line, Fe I 6302 A magnetograms, and 6563 A Hα images are used to study the relation of G-band bright points (GBPs) to magnetic elements in the photosphere. Angular resolution of 02 and 03 is achieved in the best G-band and magnetogram images, respectively. Single magnetogram sensitivity of 120-150 gauss (Φmin ~ 1016 Mx) is achieved. Small-scale GBPs appear both in intergranular lanes and on the edges of certain bright, rapidly expanding granules. The latter class of GBPs are nonmagnetic (at the flux limit) and are a source of confusion in magnetic element studies. The large-scale pattern of GBPs and magnetic flux in plage are highly correlated; GBPs occur preferentially on the periphery of extended plage regions, which are primarily demarcated by dark or neutral-contrast regions (e.g., pores or unresolved structures). On subarcsecond scales, GBPs are cospatial (to within an average of 024) and comorphous with magnetic elements in intergranular lanes; larger flux concentrations appear more diffuse than the associated GBP groupings. The average peak flux density of GBPs in the data set is ~160 gauss. No significant trend in GBP flux density as a function of either contrast or size is found. Rings of magnetic elements on 5'' scales remain very stable for periods on the order of hours. GBPs trace the temporal evolution of magnetic elements closely: there is no indication of a lead or lag (to within the 30-90 s precision of our data) in the appearance of GBPs relative to the appearance of magnetic elements. Pore formation via the accumulation of magnetic elements at a flow-field sink is seen in the data set. Magnetic elements and granules are continually advected into pores by the photospheric flow field.