Parameterising the Solar ``Surface Term'' over the Activity Cycle
Rachel Howe
University of Birmingham
W.C. Chaplin (University of Birmingham), G.R. Davies (University of Birmingham), Y. Elsworth (University of Birmingham), W. Ball (University of Goettingen), S. Basu (Yale University)
The discrepancy between model predictions and measured oscillation frequencies for solar acoustic modes includes a significant frequency-dependent term known as the surface term. We parameterise this term for data from BiSON and GONG using
the mode inertia and cubic and inverse frequency terms and look at the variation of the fitted terms over time as solar activity varies. Most of the variation is seen in the cubic term, which is potentially related to the presence of magnetic flux tubes.