Study of p-mode excitation and damping rate variations from IRIS++ observations
Abstract
11 years of low degree helioseismic data collected by the IRIS++ network (International Research of the Interior of the Sun) have been analyzed. The epoch covered (mid-1989 to end-1999) spans the maximum and the falling phase of solar cycle 22 and the rising phase of the current solar cycle 23. Annual timeseries with an overlap of 6 months are used to study the variations with solar activity of the p-mode frequencies nu n,l, heights Hn,l, and linewidths Gamma n,l, taking into account the effects of the window function. These are used to infer variations in the velocity power <Vn,l2> and the energy supply rate dot En,l which relate to changes in the excitation and the damping of the modes. We find global changes over the range 2600 <= nu <= 3600 mu Hz of about -26%, 11%, -11% for the heights, the linewidths, and the velocity power respectively, and a constant energy supply to the modes.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 2003
- DOI:
- 10.1051/0004-6361:20031014
- Bibcode:
- 2003A&A...408..729S
- Keywords:
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- Sun: helioseismology;
- Sun: activity