High-resolution spectropolarimetric observations of the temporal\n evolution of magnetic fields in photospheric bright points

Abstract

Context. Magnetic bright points (MBPs) are dynamic, small-scale magnetic\nelements often found with field strengths of the order of a kilogauss within\nintergranular lanes in the photosphere. Aims. Here we study the evolution of\nvarious physical properties inferred from inverting high-resolution full Stokes\nspectropolarimetry data obtained from ground-based observations of the quiet\nSun at disc centre. Methods. Using automated feature-tracking algorithms, we\nstudied 300 MBPs and analysed their temporal evolution as they evolved to\nkilogauss field strengths. These properties were inferred using both the NICOLE\nand SIR Stokes inversion codes. We employ similar techniques to study radiative\nmagnetohydrodynamical simulations for comparison with our observations.\nResults. Evidence was found for fast (~30 - 100s) amplification of magnetic\nfield strength (by a factor of 2 on average) in MBPs during their evolution in\nour observations. Similar evidence for the amplification of fields is seen in\nour simulated data. Conclusions. Several reasons for the amplifications were\nestablished, namely, strong downflows preceding the amplification (convective\ncollapse), compression due to granular expansion and mergers with neighbouring\nMBPs. Similar amplification of the fields and interpretations were found in our\nsimulations, as well as amplification due to vorticity. Such a fast\namplification will have implications for a wide array of topics related to\nsmall-scale fields in the lower atmosphere, particularly with regard to\npropagating wave phenomena in MBPs.\n