The activity-related variations in the solar acoustic frequencies have beenknown for 30 years. However, the importance of the different contributions isstill not well established. With this in mind, we developed an empirical modelto estimate the spot-induced frequency shifts, which takes into account thesunspot properties, such as area and latitude. The comparison between the modelfrequency shifts obtained from the daily sunspot records and those observedsuggests that the contribution from a stochastic component to the totalfrequency shifts is about 30%. The remaining 70% is related to a global,long-term variation. We also propose a new observable to investigate the short-and mid-term variations of the frequency shifts, which is insensitive to thelong-term variations contained in the data. On the shortest time scales thevariations in the frequency shifts are strongly correlated with the variationsin the total area covered by sunspots. However, a significant loss ofcorrelation is still found, which cannot be fully explained by ignoring theinvisible side of the Sun when accounting for the total sunspot area. We alsoverify that the times when the frequency shifts and the sunspot areas do notvary in a similar way tend to coincide with the times of the maximum amplitudeof the quasi-biennial variations found in the seismic data.
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