Infrared photometry of solar photospheric structures. I. Active regions atthe center of the disk

Simultaneous time series of broadband images of two active regions close to the disk center were acquired at the Swedish Vacuum Solar Telescope, La Pa lma, in the infrared bands at 1.55 and 0.80 mum, corresponding to the minim um and maximum continuum opacities, respectively. Dark faculae are detected in images obtained as weighted intensity differences between both waveleng th bands. Maps of brightness temperatures T-b (1.55 mum) and T-b (0.80 mum) were computed for the best pairs of images. In the scatter plots T-b (1.55 ) versus T-b (0.80), the elements of quiet regions can be dearly distinguis hed from those of faculae and gores, while the transition between faculae a nd pores is smooth. The temperature difference T-b(1.55) - T-b(0.80) in fac ulae is lower than that in the quiet photosphere but increases with decreas ing T-b and is higher inside pores. Most of the pores are surrounded by rin glike regions of low temperature difference. The minimum intensity of pores at both wavelengths decreases with increasing diameter. Maps of horizontal motions of dark faculae and pores were derived from time series of intensi ty-difference images, using the local correlation tracking technique. Veloc ities corresponding to large-scale separation of polarities, an emergence o f magnetic flux, twist and contraction related to a pore formation, shear m otions, and a twist in dark faculae were measured.