Granular Scale Magnetic Flux Cancellations as Observed with the Hinode/SOT

The mutual loss of magnetic flux due to the apparent collision of opposite-polarity magnetic elements is called ``magnetic flux cancellation'' as a descriptive term. The flux cancellation is essential to understand the dissipation of magnetic flux from the solar surface. We investigate the evolution of 5 granular-scale flux cancellations just outside the moat region of a sunspot by using accurate spectropolarimetric measurements with the Solar Optical Telescope aboard Hinode. We find that the opposite-polarity magnetic elements approach a junction of the intergranular lanes and then they collide with each other there. The intergranular junction has Doppler red shifts, darker intensities than the regular intergranular lanes, and surface converging flows. We also find that the horizontal magnetic field appears between the canceling elements in only one event. The horizontal fields are observed along the intergranular lanes with red shifts. This cancellation is most probably a result of the submergence of low-lying photospheric magnetic flux. In the other 4 events, the horizontal field is not observed between the opposite-polarity magnetic elements at any time when they approach and cancel each other. These canceling elements have nearly vertical fields even while they are in contact each other. These events are more interesting because in the usual idea of the submergence of a low lying Ω-loop or the buoyant rise of a U-loop, the appearance of a horizontal field is the observational signature of the loop top (or bottom) passing across the photosphere. Our observational results suggest the possibility that the actual flux cancellation is highly time dependent events near the solar surface at scales less than a pixel of Hinode/SOT (about 200 km). Observations with a spatial resolution higher than Hinode/SOT are essential to reveal physical process of the dissipation of magnetic flux on the Sun.