The role of magnetic flux variations in the evolution of EUV bright points

We report three types of evolutions of EUV bright points (EBPs) which are characterized by their height variations. We analyzed three EBPs during their lifetimes observed by STEREO/SECCHI/EUVI and we obtained heights, sizes, and intensities. Moreover, we investigated their underlying magnetic bipoles observed by SOHO/MDI and we measured distances and fluxes of the two opposite fragments. We found three distinct changes in the heights of the EBPs: upward, downward, and flat. In the upward case, the EBP showed a small and dark structure first, and then changed to a large and bright loop. In the downward case, the EBP first appeared as a large and dark loop structure, and then evolved to a compact and bright loop system. Finally, in the flat case, the height and the size of the EBP didn't change significantly. We found that those EBPs were associated with three distinct contact types of their underlying magnetic fragments, emerging, cancelling, and shearing, respectively. In all cases, both flux emergences and flux cancellations were observed during the lifetimes of the BPs. The flux emergence was dominant in the initial phase and the flux cancellation was significant when the intensity reached its maximum. In addition, we found a remarkable correlation between the heights of the EBPs and the distance of the opposite magnetic fragments.