Tag Archives: solar cycle

15. Potential field source surface “breathes” over the course of the solar cycle

Contributed by WIlliam Arden. Posted on May 15, 2014

Our results show that raising the source surface height 15-30% during solar minimum (depending on the model used) better reproduces the observed IMF open flux from OMNI. We used two different PFSS models and the MDI/HMI magnetograms as input.

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

Contributed by Fraser Watson. Posted on April 25, 2014

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.