Solar neutrinos, helioseismology and the solar internal dynamics

Neutrinos are fundamental particles ubiquitous in the Universe. Their properties remain elusive despite more than 50 years of intense research activity. In this review we remind the reader of the noticeable properties of these particles and of the stakes of the solar neutrino puzzle. The Standard Solar Model triggered persistent efforts in fundamental Physics to predict the solar neutrino fluxes, and its constantly evolving predictions have been regularly compared to the detected neutrino signals. Anticipating that this standard model could not reproduce the internal solar dynamics, a SEismic Solar Model was developed which enriched theoretical neutrino flux predictions with in situ observation of acoustic waves propagating in the Sun. This review reminds the historical steps, from the pioneering Homestake detection, the GALLEX- SAGE captures of the first pp neutrinos and emphasizes the importance of the Superkamiokande and SNO detectors to demonstrate that the solar-emitted electronic neutrinos are partially transformed into other neutrino flavors before reaching the Earth. The success of BOREXINO in detecting the 7 Be neutrino signal justifies the building of a new generation of detectors to measure the entire solar neutrino spectrum. A coherent picture emerged from neutrino physics and helioseismology. Today, new paradigms take shape: determining the masses of neutrinos and the research on the Sun is focusing on the dynamical aspects and on signature of dark matter. The third part of the review is dedicated to this prospect. The understanding of the crucial role of both rotation and magnetism in solar physics benefit from SoHO, SDO, and PICARD space observations. For now, the particle and stellar challenges seem decoupled, but this is only a superficial appearance. The development of asteroseismology shows the far-reaching impact of Neutrino and Stellar Astronomy.Comment: 60 pages, 12 figures Invited review in press in Report on Progress in Physic

Seismic sensitivity to sub-surface solar activity from 18 years of GOLF/SoHO observations

Solar activity has significantly changed over the last two Schwabe cycles. After a long and deep minimum at the end of Cycle 23, the weaker activity of Cycle 24 contrasts with the previous cycles. In this work, the response of the solar acoustic oscillations to solar activity is used in order to provide insights on the structural and magnetic changes in the sub-surface layers of the Sun during this on-going unusual period of low activity. We analyze 18 years of continuous observations of the solar acoustic oscillations collected by the Sun-as-a-star GOLF instrument onboard the SoHO spacecraft. From the fitted mode frequencies, the temporal variability of the frequency shifts of the radial, dipolar, and quadrupolar modes are studied for different frequency ranges which are sensitive to different layers in the solar sub-surface interior. The low-frequency modes show nearly unchanged frequency shifts between Cycles 23 and 24, with a time evolving signature of the quasi-biennial oscillation, which is particularly visible for the quadrupole component revealing the presence of a complex magnetic structure. The modes at higher frequencies show frequency shifts 30% smaller during Cycle~24, which is in agreement with the decrease observed in the surface activity between Cycles 23 and 24. The analysis of 18 years of GOLF oscillations indicates that the structural and magnetic changes responsible for the frequency shifts remained comparable between Cycle 23 and Cycle 24 in the deeper sub-surface layers below 1400 km as revealed by the low-frequency modes. The frequency shifts of the higher-frequency modes, sensitive to shallower regions, show that Cycle 24 is magnetically weaker in the upper layers of Sun.Comment: Accepted for publication in A&

Interpreting the Atmospheric Neutrino Anomaly

We suggest that the atmospheric neutrino anomaly observed in the Super-Kamiokande (and other) experiments results from the combined effects of muon-neutrino to tau-neutrino oscillations with a Delta m^2 value of approximately 0.4 eV^2 and oscillations between muon neutrinos and electron neutrinos (and vice-versa) with 0.0001 < Delta m^2 < 0.001 eV^2. With an appropriate choice of a three-neutrino mixing matrix, such a hypothesis is consistent with essentially all neutrino observations.Comment: 12 pages, 2 eps figures, Latex2e, elsart style, submitted to Physics Letters B --REV2-- Updated figure 1 and added figure 2: Super-K single R dat

Probing the internal solar magnetic field through g-modes

The observation of g-mode candidates by the SoHO mission opens the possibility of probing the internal structure of the solar radiative zone (RZ) and the solar core more directly than possible via the use of the p-mode helioseismology data. We study the effect of rotation and RZ magnetic fields on g-mode frequencies. Using a self-consistent static MHD magnetic field model we show that a 1% g-mode frequency shift with respect to the Solar Seismic Model (SSeM) prediction, currently hinted in the GOLF data, can be obtained for magnetic fields as low as 300 kG, for current measured modes of radial order n=-20. On the other hand, we also argue that a similar shift for the case of the low order g-mode candidate (l=2, n=-3) frequencies can not result from rotation effects nor from central magnetic fields, unless these exceed 8 MG.Comment: 6 pages, 2 figures; final version to appear in MNRA