Damping and Excitation Variations of the Solar Acoustic Modes Using LOWL Observations

We have used observations made with the helioseismic instrument LOWLcollected over $\sim$ 6 years to carry out an independent study of thevariations of the p-mode damping and excitation rates with solar activity. Weobserve significant variations in the mode height, mode width and mode velocitypower over a wide range of angular degree values. Their sensitivities to solaractivity show clear evidence of frequency dependence, the modes in thefrequency range from 2700 and 3300 $\mu$Hz showing the largest variations andexhibiting a maximum change centered around 3100 $\mu$Hz. As for the modeenergy supply rate, it is consistent, at the level of precision of theobservations, with a zero change along the solar cycle and over the range ofstudied frequencies. Moreover, the variations with solar activity of each ofthese parameters are observed to be more or less $\ell$-independent over therange of studied angular degrees. Our results provide the first in-depthconfirmation of the findings obtained from GONG measurements for intermediateangular degrees.Comment: 29 pages, 8 figures, Accepted for publication in Ap