Time-frequency analysis of GALLEX and GNO solar neutrino data

Time-frequency analysis of data from the GALLEX and GNO solar neutrino experiments shows that some features in power-spectrum analyses of those datasets are due to aliasing (a result of the fact that run durations tend to be small multiples of one week). Displays formed from the published GALLEX data show a sharp discontinuity that we attribute to some systematic effect. We therefore normalize data for each of the four experiments in the GALLEX series and concatenate the resulting normalized data. This step effectively removes the presumed systematic effect. To help understand the effect of aliasing, we form time-frequency displays of the two principal modulations found in the data, at 11.87 year(-1) and at 13.63 year(-1). We also form time-frequency displays of datasets formed by subtracting these modulations from the actual (normalized) data. The results suggest that the true principal modulation is that at 11.87 year(-1). Comparison with helioseismology data suggests that modulation may be occurring in the core, perhaps resulting from inhomogeneities and fluctuations in the nuclear-burning process, and that the sidereal rotation rate of the core is 12.87 year(-1), or 408 nHz.