Damping and excitation variations of the solar acoustic modes using LOWL observations

Abstract

We have used observations made with the helioseismic instrument LOWL collected over $\sim$ 6 years to carry out an independent study of the variations of the p-mode damping and excitation rates with solar activity. We observe significant variations in the mode height, mode width and mode velocity power over a wide range of angular degree values. Their sensitivities to solar activity show clear evidence of frequency dependence, the modes in the frequency range from 2700 and 3300 $\mu$Hz showing the largest variations and exhibiting a maximum change centered around 3100 $\mu$Hz. As for the mode energy supply rate, it is consistent, at the level of precision of the observations, with a zero change along the solar cycle and over the range of studied frequencies. Moreover, the variations with solar activity of each of these parameters are observed to be more or less $\ell$-independent over the range of studied angular degrees. Our results provide the first in-depth confirmation of the findings obtained from GONG measurements for intermediate angular degrees.