282 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
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
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
Impact of the physical processes in the modeling of HD49933
Context : On its asteroseismic side, the initial run of CoRoT was partly
devoted to the solar like star HD49933.The eigenmodes of this F dwarf have been
observed with unprecedented accuracy.
Aims : We investigate quantitatively the impact of changes in the modeling
parameters like mass and composition. More importantly we investigate how a
sophisticated physics affects the seismological picture of HD49933. We consider
the effects of diffusion, rotation and the changes in convection efficiency.
Methods : We use the CESAM stellar evolution code coupled to the ADIPLS
adiabatic pulsation package to build secular models and their associated
oscillation frequencies. We also exploited the hydrodynamical code STAGGER to
perform surface convection calculations. The seismic variables used in this
work are : the large frequency separation, the derivative of the surface phase
shift,and the eigenfrequencies and .
Results : Mass and uncertainties on the composition have much larger impacts
on the seismic variables we consider than the rotation. The derivative of the
surface phase shift is a promising variable for the determination of the helium
content. The seismological variables of HD49933 are sensitive to the assumed
solar composition and also to the presence of diffusion in the models.Comment: 7 pages, 3 figures, 7 table
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