Apparent latitudinal modulation of the solar neutrino flux

We examine the solar neutrino flux, as measured by the Homestake neutrino detector, to search for evidence of a dependence upon the solar latitude of the Earth-Sun line that varies from 7.degrees 25 south in mid-March to 7.degrees 25 north in mid-September. Although the flux does not obviously show any dependence on latitude, we do find evidence for a dependence of the variance of the flux upon latitude. When data from 108 runs of the Homestake experiment are divided into four quartiles, sorted according to latitude, we find that the northernmost quartile exhibits a larger variance than the other three. By applying the shuffle test, we estimate the probability that this could have occurred by chance to be in the range 1%-2%. For more detailed information, we examine a "reconstructed flux" formed from our recent maximum likelihood spectrum analysis. This procedure indicates that the variance is largest at about 6.degrees 5 north. We also find that the spectrum of the variance of the reconstructed flux has a notable peak at 1 cycle y(-1) tending to confirm a latitude dependence of the variance. We also examine the 12.88 cycle yr periodicity described in our recent paper: and find that the amplitude of the periodicity is greater for the northernmost quartile than for the other quartiles. We suggest that these effects may be attributed to resonant spin-favor precession of left-hand-helicity electron neutrinos in the magnetic field of the solar radiative zone.