34th Solar Physics Division Meeting, June 2003
Session 26 The Changing Solar interior II
Oral, Friday, June 20, 2003, 9:00am-12:00noon, Auditorium

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[26.05] Variability of the Solar Neutrino Flux

P.A. Sturrock (Stanford University)

The question of variability of the solar neutrino flux is important for particle physics and also for solar physics. It is generally believed that the solar neutrino flux is constant and that the deficit can be explained by the MSW (Mikhevev-Smirnov-Wolfenstein) effect which converts electron neutrinos into mu or tau neutrinos as they propagate through the dense solar interior. Variability of the neutrino flux would indicate that the MSW effect must be supplemented by some other process such as Resonant Spin-Flavor Precession (RSFP) that changes a neutrino into an antineutrino of different flavor. This process can explain variability since it involves the Sunís internal magnetic field. If (as is likely) the magnetic field is not cylindrically symmetric, the RSFP process would lead to modulation at the synodic rotation frequency and/or a harmonic of this frequency.

We present the results of time-series analysis of solar-neutrino data from the Homestake, GALLEX-GNO, SAGE, and Super-Kamiokande experiments. We find evidence for modulation at 12.88 y-1, consistent with the rotation rate of the radiative zone, at 13.59 y-1, consistent with the rotation rate of the deep convection zone, and at 26.57 y-1, consistent with the harmonic of the rotation rate at or near the tachocline. We present estimates of the statistical significance of these results, and we discuss the significance of the bimodal structure of the histogram of GALLEX-GNO flux estimates.

If the present evidence for variability of the solar neutrino flux is substantiated by future analysis of additional data, neutrino measurements may yield new insight into the strength, structure, and variability of the Sunís internal magnetic field.

This work was supported by the National Science Foundation.

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.