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