323 research outputs found
The solar energetic balance revisited by young solar analogs, helioseismology and neutrinos
The energetic balance of the Standard Solar Model (SSM) results from an
equilibrium between nuclear energy production, energy transfer, and
photospheric emission. In this letter, we derive an order of magnitude of
several % for the loss of energy in kinetic energy, magnetic energy, and X or
UV radiation during the whole solar lifetime from the observations of the
present Sun. We also estimate the mass loss from the observations of young
solar analogs which could reach up to 30% of the current mass. We deduce new
models of the present Sun, their associated neutrino fluxes, and their internal
sound-speed profile. This approach sheds quantitative lights on the
disagreement between the sound speed obtained by helioseismology and the sound
speed derived from the SSM including the updated photospheric CNO abundances,
based on recent observations. We conclude that about 20% of the present
discrepancy could come from the incorrect description of the early phases of
the Sun, its activity, its initial mass and mass-loss history. This study has
obvious consequences on the solar system formation and the early evolution of
the closest planets.Comment: 14 pages, 3 figures; Published in ApJ lett 201
Laboratory performances of the solar multichannel resonant scattering spectrometer prototype of the GOLF-New Generation instrument
This article quickly summarizes the performances and results of the GOLF/SoHO
resonant spectrometer, thus justifying to go a step further. We then recall the
characteristics of the multichannel resonant GOLF-NG spectrometer and present
the first successful performances of the laboratory tests on the prototype and
also the limitations of this first technological instrument. Scientific
questions and an observation strategy are discussed.Comment: 8 pages, 8 figures, published in Astronomical Note
Concluding remarks on Solar and Stellar Activities and related planets
The symposium has shown the dynamism of this rapidly evolving discipline. I
shall concentrate here on some highlights and some complementary informations.
I conclude on open questions with some perspectives on solar & stellar activity
and related planets.Comment: 17 pages, 13 figures, concluding remarks of IAU264 in RIO, 200
Solar neutrino physics oscillations: Sensitivity to the electronic density in the Sun's core
Solar neutrinos coming from different nuclear reactions are now detected with
a high statistics. Consequently, an accurate spectroscopic analysis of the
neutrino fluxes arriving on the Earth's detectors become available, in the
context of neutrino oscillations. In this work, we explore the possibility of
using this information to infer the radial profile of the electronic density in
the solar core. So, we discuss the constraints on the Sun's density and
chemical composition that can be determined from solar neutrino observations.
This approach constitutes an independent and alternative diagnostic to the
helioseismic investigations already done. The direct inversion method, that we
propose to get the radial solar electronic density profile, is almost
independent of the solar model.Comment: 9 pages, 5 figures, 1 tabl
Probing the Existence of a Dark Matter Isothermal Core Using Gravity Modes
Although helioseismology has been used as an effective tool for studying the
physical mechanisms acting in most of the solar interior, the microscopic and
dynamics of the deep core is still not well understood. Helioseismological
anomalies may be partially resolved if the Sun captures light, non-annihilating
dark matter particles, a currently discussed dark matter candidate that is
motivated by recent direct detection limits. Once trapped, such particles (4-10
GeV) naturally fill the solar core. With the use of a well-defined stellar
evolution code that takes into account an accurate description of the capture
of dark matter particles by the Sun, we investigate the impact of such
particles in its inner core. Even a relatively small amount of dark matter
particles in the solar core will leave an imprint on the absolute frequency
values of gravity modes, as well as the equidistant spacing between modes of
the same degree. The period separation for gravity modes could reveal changes
of up to 3% for annihilating dark matter and of up to 20% for non-annihilating
dark matter. This effect is most pronounced in the case of the gravity dipole
(l=1) modes.Comment: Article published in The Astrophysical Journal Letters, 5 pages and 4
figure
Review of Solar and Reactor Neutrinos
Over the last several years, experiments have conclusively demonstrated that
neutrinos are massive and that they mix. There is now direct evidence for
s from the Sun transforming into other active flavors while en route to
the Earth. The disappearance of reactor s, predicted under the
assumption of neutrino oscillation, has also been observed. In this paper,
recent results from solar and reactor neutrino experiments and their
implications are reviewed. In addition, some of the future experimental
endeavors in solar and reactor neutrinos are presented.Comment: Proceedings of the XXII International Symposium on Lepton and Photon
Interactions at High Energy (Lepton-Photon 2005, June 30 to July 5, 2005,
Uppsala, Sweden). 11 figures, 5 table
Seismic and dynamical solar models i-the impact of the solar rotation history on neutrinos and seismic indicators
Solar activity and helioseismology show the limitation of the standard solar
model and call for the inclusion of dynamical processes in both convective and
radiative zones. We concentrate here on the radiative zone and first show the
sensitivity of boron neutrinos to the microscopic physics included in solar
models. We confront the neutrino predictions of the seismic model to all the
detected neutrino fluxes. Then we compute new models of the Sun including a
detailed transport of angular momentum and chemicals due to internal rotation
that includes meridional circulation and shear induced turbulence. We use two
stellar evolution codes: CESAM and STAREVOL to estimate the different terms. We
follow three temporal evolutions of the internal rotation differing by their
initial conditions: very slow, moderate and fast rotation, with magnetic
braking at the arrival on the main sequence for the last two. We find that the
meridional velocity in the present solar radiative zone is extremely small in
comparison with those of the convective zone, smaller than 10^-6 cm/s instead
of m/s. All models lead to a radial differential rotation profile but with a
significantly different contrast. We compare these profiles to the presumed
solar internal rotation and show that if meridional circulation and shear
turbulence were the only mechanisms transporting angular momentum within the
Sun, a rather slow rotation in the young Sun is favored. The transport by
rotation slightly influence the sound speed profile but its potential impact on
the chemicals in the transition region between radiation and convective zones.
This work pushes us to pursue the inclusion of the other dynamical processes to
better reproduce the present observable and to describe the young active Sun.
We also need to get a better knowledge of solar gravity mode splittings to use
their constraints.Comment: 39 pages, 9 figures, accepted in Astrophysical Journa
Coriolis force corrections to g-mode spectrum in 1D MHD model
The corrections to g-mode frequencies caused by the presence of a central
magnetic field and rotation of the Sun are calculated. The calculations are
carried out in the simple one dimensional magnetohydrodynamical model using the
approximations which allow one to find the purely analytical spectra of
magneto-gravity waves beyond the scope of the JWKB approximation and avoid in a
small background magnetic field the appearance of the cusp resonance which
locks a wave within the radiative zone. These analytic results are compared
with the satellite observations of the g-mode frequency shifts which are of the
order one per cent as given in the GOLF experiment at the SoHO board. The main
contribution turns out to be the magnetic frequency shift in the strong
magnetic field which obeys the used approximations. In particular, the fixed
magnetic field strength 700 KG results in the mentioned value of the frequency
shift for the g-mode of the radial order n=-10. The rotational shift due to the
Coriolis force appears to be small and does not exceed a fracton of per cent,
\alpha_\Omega < 0.003.Comment: RevTeX4, 9 pages, 4 eps figures; accepted for publication in
Astronomy Reports (Astronomicheskii Zhurnal
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