TINY PORES OBSERVED BY HINODE/SOLAR OPTICAL TELESCOPE

The study of pores, small penumbraless sunspots, can give us a chance to understand how strong magnetic fields interact with convective motions in the photosphere. For a better understanding of this interaction, we investigate the temporal variation of several tiny pores smaller than 2 ''. These pores were observed by the Solar Optical Telescope on board Hinode on 2006 December 29. We have analyzed the high-resolution spectropolarimetric (SP) data and the G-band filtergrams taken during the observation. Magnetic flux density and Doppler velocities of the pores are estimated by applying the center-of-gravity method to the SP data. The horizontal motions in and around the pores are tracked by adopting the nonlinear affine velocity estimator method to the G-band filter images. As a result, we found the following. (1) The darkness of the pores is positively correlated with the magnetic flux density. (2) Downflows always exist inside and around the pores. (3) The speed of downflows inside the pores is negatively correlated with their darkness. (4) The pores are surrounded by strong downflows. (5) Brightness changes of the pores are correlated with the divergence of mass flow (correlation coefficient > 0.9). (6) The pores in the growing phase are associated with the converging flow pattern and the pores in the decay phase with the diverging flow pattern. Our results support the idea that a pore grows as the magnetic flux density increases due to the convergence of ambient mass flow and it decays with the decrease of the flux density due to the diverging mass flow.