  High cadence, multiwavelength, optical observations of solar magnetic bright
points, captured at disk center using the ROSA and IBIS imaging systems on the
Dunn Solar Telescope, are presented. Magnetic bright points manifesting in the
Na I D1 core are found to preferentially exist in regions containing strong
downflows, in addition to co-spatial underlying photospheric magnetic field
concentrations. Downdrafts within Na I D1 bright points exhibit speeds of up to
7km/s, with preferred structural symmetry in intensity, magnetic field and
velocity profiles about the bright point center. Excess intensities associated
with G-band and Ca II K observations of magnetic bright points reveal a
power-law trend when plotted as a function of magnetic flux density. However,
Na I D1 observations of the same magnetic features indicate an intensity
plateau at weak magnetic field strengths below ~150G, suggesting the presence
of a two-component heating process; one which is primarily acoustic, the other
predominantly magnetic. We suggest that this finding is related to the physical
expansion of magnetic flux tubes, with weak field strengths (~50G) expanding by
~76%, compared to a ~44% expansion when higher field strengths (~150G) are
present. These observations provide the first experimental evidence of rapid
downdrafts in Na I D1 magnetic bright points, and reveal the nature of a
previously unresolved intensity plateau associated with these structures.
