that while the mode energy decreases with activity the energy supply rate shows no solar cycle variation [e.g. @2000MNRAS.313...32C; @2000ApJ...543..472K; @2001ESASP.464...71A; @2001ESASP.464..123T; @2002SoPh..209..247J; @2003ApJ...588.1204H; @2004ApJ...604..969J; @2006ApJ...650..451S]. Therefore, the observed variations in mode energy and mode power probably arise from an increase in damping only. As the energy of the modes decreases between solar minimum and solar maximum this implies that some energy has gone missing.

One potential source of damping is magnetic activity on the solar surface. Active regions are known to suppress the power of p modes, and effect lifetimes, and energy supply rates [e.g. @1981SoPh...69..233W; @1982ApJ...253..386L; @1992ApJ...394L..65B; @2001ApJ...563..410R; @2002ApJ...572..663K; @2004ApJ...608..562H]. However, the associated mechanisms are not yet fully understood. One explanation is that strong-field magnetic regions, such as sunspots, are effective absorbers of p-mode power . @2000ApJ...543..472K suggested that the energy could be in flux tubes, whose numbers increase with solar activity, and the energy could excite oscillations in magnetic elements. Another suggestion is that the efficiency of mode excitation is reduced in magnetic areas [e.g. @1988ApJ...326..462G; @1995ApJ...451..372C; @1996ApJ...464..476J]. Other possible explanations as to why p-mode excitation is suppressed in sunspots include a different height of spectral line formation due to the Wilson depression or a modification of 