Rotational signature and possible r-mode signature in the GALLEX solar neutrino data

Recent analysis of the Homestake data has yielded evidence that the solar neutrino flux varies in time-more specifically, that it exhibits a periodic variation that may be attributed to rotational modulation occurring deep in the solar interior, either in the tachocline or in the radiative zone. Here we present a spectral analysis of the GALLEX data that yields supporting evidence for this rotational modulation. The most prominent peak in the power spectrum occurs at the synodic frequency of 13.08 yr(-1) (cycles per year) and is estimated to be significant at the 0.1% level. It appears that the most likely interpretation of this modulation is that the electron neutrinos have nonzero magnetic moment, so that they oscillate between left-hand (detectable) and right-hand (nondetectable) chiralities as they traverse the Sun's internal magnetic field. This oscillation could account for the neutrino deficit. The second strongest peak in the GALLEX spectrum has a period of 52 days, and this period occurs in other solar data as well. We suggest that this periodicity and also the Rieger 154 day periodicity, which shows up in many solar parameters and in the Homestake data, are due to r-mode oscillations.