AAS 200th meeting, Albuquerque, NM, June 2002
Session 89. Solar Internal Structure and Dynamics
Oral, Thursday, June 6, 2002, 2:00-3:30pm, Mesilla

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[89.04] Variability of the Solar Neutrino Flux

P.A. Sturrock (Center for Space Science and Astrophysics, Stanford University), J.D. Scargle (NASA/Ames Research Center), G. Walther (Statistics Department, Stanford University), M.A. Weber (Center for Space Science and Astrophysics, Stanford University), M.S. Wheatland (Physics Department, Sydney University, Australia)

Several tests of the available data provide evidence for variability of the solar neutrino flux. The variance of the Homestake measurements is larger than expected of a constant flux, and varies with heliographic latitude. The Homestake power spectrum contains a peak at 12.88 y-1 (period 28.4 days), corresponding to a sidereal rotation frequency of 440 nHz, close to that of the radiative zone. The power spectrum of GALLEX-GNO data contains the 12.88 y-1 peak and a stronger peak at 13.59 y-1 (period 26.9 days), corresponding to a sidereal rotation frequency of 462 nHz, that of the equatorial convection zone at normalized radius 0.85. Further evidence for time variation comes from the bimodality of the GALLEX-GNO and SAGE histograms. Joint spectrum analysis of the Homestake and GALLEX-GNO data yields evidence for the influence of r-mode oscillations [with l = 3, m = {1,2,3}] associated with the same sidereal rotation rate (13.88 y-1 or 440 nHz) found previously. The periods of these oscillations (158, 79, and 53 days, respectively) are close to those of known Rieger-type oscillations, and therefore point to the radiative zone as the source of these oscillations.

A subset of these tests, selected to be independent, yield results that could arise by chance from a constant flux with probabilities ranging from 0.1 to 0.0001. If there are no relevant experimental systematic effects, and if the tests are valid and statistically independent, the combined estimates yield a probability of 10-15 that the results are compatible with a constant flux. A variable flux implies that neutrinos have a significant magnetic moment, and that neutrino measurements may be used to probe the Sun's internal magnetic field and internal dynamics.

This work was supported by NASA grants NAS 8-37334 and NAG 5-9784, NSF grant AST-0097128, and the NASA Applied Information Systems Research Program.

The author(s) of this abstract have provided an email address for comments about the abstract: sturrock@stanford.edu

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.