Line Asymmetries Above and Below the Acoustic Cut-Off Frequency and the Excitation of Solar Oscillations

Lead Investigator:
Rakesh Nigam

Team Members:
Dr. P.H. Scherrer

Technical Summary:

The power spectrum of solar oscillation modes shows varying amounts of asymmetry. In helioseismology the eigenfrequencies were determined by assuming that the power spectrum was symmetric and can be fitted by a Lorentzian. This leads to systematic errors in the determination of mode frequencies. The line asymmetry occurs whenever the waves are excited by a localized source. Nigam and Kosovichev (1996) have shown that the sense and the degree of the asymmetry depend on the location and on the type of the excitation source. Therefore, studying the line asymmetry will enable us to improve the frequency measurements, find the depth, latitudinal distribution and the physical nature of these localized sources that are responsible for exciting the solar modes of different types and also investigate other aspects of nonadiabaticity which get neglected when asymmetry is ignored.


Complete text of proposal.