Small-Scale Magnetic-Flux Emergence Observed with Hinode Solar Optical Telescope

We observed small-scale magnetic-flux emergence in a sunspot moat region by the Solar Optical Telescope (SOT) aboard the Hinode satellite. We analyzed filtergram images observed at wavelengths of Fe 6302 Å, G band, and Ca II H. In StokesI images of Fe 6302 Å, emerging magnetic flux was recognized as dark lanes. In the G band, they showed to be their shapes almost the same as in StokesI images. These magnetic fluxes appeared as dark filaments in Ca II H images. StokesV images of Fe 6302 Å showed pairs of opposite polarities at footpoints of each filament. These magnetic concentrations were identified to correspond to bright points in G band/Ca II H images. From an analysis of time-sliced diagrams, we derived the following properties of emerging flux, which are consistent with those of previous studies: (1) Two footpoints separate each other at a speed of 4.2 kms⁻¹ during the initial phase of evolution, and decrease to about 1 kms⁻¹ 10 minutes later. (2) Ca II H filaments appear almost simultaneously with the formation of dark lanes in StokesI in an observational cadence of 2 minutes. (3) The lifetime of the dark lanes in the Stokes I and G band is 8 minutes, while that of Ca filament is 12 minutes. An interesting phenomena was observed, that an emerging flux tube expanded laterally in the photosphere with a speed of 3.8 kms⁻¹. A discussion on the horizontal expansion of the flux tube is given with refernce to previous simulation studies.