Tag Archives: magnetic fields
11. The long-term trend in magnetic fields of sunspot umbrae
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.