Tracing the "acoustic'' solar cycle: A direct comparison of BiSON and GOLF low-l p-mode variations

We present a detailed, comparative study of low angular degree solar p-mode variations extracted by analyses of two sets of observational data. These were collected by the ground-based Birmingham Solar-Oscillations Network (BiSON) and the Global Oscillations at Low Frequency (GOLF) instrument on board the ESA/NASA SOHO satellite. The similar to5.5 yr period analyzed covers the complete rising phase of solar activity cycle 23 ( 1996 2002). We find an excellent level of agreement in the uncovered variations, indicating that the two data sets are highly correlated and dominated by the same mode realization noise (the signature of the stochastic forcing of the resonances). The results lend further support to the surmise that changes in damping alone may account for observed variations in mode power and damping. While significant variations in peak asymmetry are uncovered in the near-continuous GOLF set, a similar analysis of the BiSON database yields a null result. This reflects the deleterious impact of its ground-based window function on the precision with which the asymmetry can be determined. As such we are unable to rule out the possibility that variations of magnitude similar to those in GOLF may be present in the BiSON observations.