We have seen that the quiescent photospheric magnetic field is composed of multiple connective scales. The observed scales range from a few megameters to those that are 100 –250 Mm in scale. We expect that the latter of these scales belongs to a spatially large, deep and hence slowly overturning convective flow — one that possibly reaches to the bottom of convection zone.
I investigate the possible long term decrease in umbral magnetic field strengths from 1998-2006. Whereas a decrease of 800 Gauss in umbral magnetic fields has been reported between 1998 and 2012, the HMI and MDI data indicate a decrease of only around 300 Gauss. The continuing availability of the excellent HMI data set will allow us to continue to refine this study as solar cycle 24 evolves.