Evolution of photospheric pores in the magnetic field

We describe conditions of pore formation in relation to the configuration and intensity of magnetic field. We use observations of the SDO/HMI instrument, which observes the photosphere in continuum and simultaneously the magnetic field with a spatial resolution of better than 1" and a temporal resolution of 45 s. We analyze a time-sequence of evolution of area and brightness of pores, their statistics, and in parallel a time-sequence of the line-of-sight magnetic field intensity and its correlation with the area and brightness. Sunspot observations from the Hurbanovo Observatory are used for the selection of a suitable area on the solar disc. A pore (small sunspot) observed near the central meridian at the Hurbanovo Observatory on October 11, 2013 was selected for analysis. We chose from each SDO image only area with a diameter of 1.05° (35" as seen from the Earth). Points of the area were transformed into rectangular coordinates (Δl, b) and for the alignment of individual images we found from the movement of a pore the synodical rotational speed: ω = 14.35°/24 hours, which is by 1°/24 higher than the tabular value. We traced the selected area from 22:01:30 h UT (October 10, 2013) to 20:01:30 h UT (October 11, 2013) in 83 images with a temporal resolution of 15 minutes. Evolution of the area was analyzed using an animation and quantitative results are derived from data files. At least 6 pores appeared in the area during the reported period. Pores are visible if a ratio p (p = intensity in the pore/background intensity) decreases below 0.85. The background noise is at a level of 5% (granulation). The magnetic induction is at the same time approximately 600 Gauss. The maximum diameter of the pores is of about 5" (10 pixels), the minimum value of p is 0.49 when B = 1200 Gauss. The course of evolution is presented in a tabular form. Aim of the analysis is demonstrated also using selected images from SDO in cooperation with CTS-UNINOVA/CA3 (Caparica, Portugal).