227 research outputs found
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
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
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
Low-Degree High-Frequency p and g Modes in the Solar Core
Solar gravity (g) modes propagate within the radiative part of the solar
interior and are highly sensitive to the physical conditions of the solar core.
They would represent the best tool to infer the structure and dynamics of the
radiative interior, in particular the core, if they were properly detected and
characterized. Although individual rotational splittings for g modes have not
yet been calculated, we have to understand the effect of these modes, and also
low-degree high-frequency p modes, on the inversion of the solar rotation rate
between 0.1 and 0.2 Rs. In this work, we follow the methodology developed in
Mathur et al. (2008) and Garcia et al. (2008), adding g modes and low-degree
high-frequency p modes to artificial inversion data sets, in order to study how
they convey information on the solar core rotation.Comment: To appear in "Magnetic Coupling between the Interior and the
Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten, Astrophysics and
Space Science Proceedings, Springer-Verlag, Heidelberg, Berlin, 200
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
Sensitivity of helioseismic gravity modes to the dynamics of the solar core
The dynamics of the solar core cannot be properly constrained through the
analysis of acoustic oscillation modes. Gravity modes are necessary to
understand the structure and dynamics of the deepest layers of the Sun. Through
recent progresses on the observation of these modes -- both individually and
collectively -- new information could be available to contribute to inferring
the rotation profile down inside the nuclear burning core. To see the
sensitivity of gravity modes to the rotation of the solar core. We analyze the
influence of adding the splitting of one and several g modes to the data sets
used in helioseismic numerical inversions. We look for constraints on the
uncertainties required in the observations in order to improve the derived core
rotation profile. We compute forward problems obtaining three artificial sets
of splittings derived for three rotation profiles: a rigid profile taken as a
reference, a step-like and a smoother profiles with higher rates in the core.
We compute inversions based on Regularized Least-Squares methodology (RLS) for
both artificial data with real error bars and real data. Several sets of data
are used: first we invert only p modes, then we add one and several g modes to
which different values of observational uncertainties (75 and 7.5 nHz) are
attributed. For the real data, we include g-mode candidate, l=2, n=-3 with
several splittings and associated uncertainties. We show that the introduction
of one g mode in artificial data improves the rate in the solar core and give
an idea on the tendency of the rotation profile. The addition of more g modes
gives more accuracy to the inversions and stabilize them. The inversion of real
data with the g-mode candidate gives a rotation profile that remains unchanged
down to 0.2 R, whatever value of splitting we attribute to the g mode.Comment: Accepted for publication in A&A, 8 pages, 11 figure
The Quasi-Biennial Periodicity (QBP) in velocity and intensity helioseismic observations
We looked for signatures of Quasi-Biennial Periodicity (QBP) over different
phases of solar cycle by means of acoustic modes of oscillation. Low-degree
p-mode frequencies are shown to be sensitive to changes in magnetic activity
due to the global dynamo. Recently have been reported evidences in favor of
two-year variations in p-mode frequencies. Long high-quality helioseismic data
are provided by BiSON (Birmingham Solar Oscillation Network), GONG (Global
Oscillation Network Group), GOLF (Global Oscillation at Low Frequency) and
VIRGO (Variability of Solar IRradiance and Gravity Oscillation) instruments. We
determined the solar cycle changes in p-mode frequencies for spherical degree
l=0, 1, 2 with their azimuthal components in the frequency range 2.5 mHz < nu <
3.5 mHz. We found signatures of QBP at all levels of solar activity in the
modes more sensitive to higher latitudes. The signal strength increases with
latitude and the equatorial component seems also to be modulated by the 11-year
envelope. The persistent nature of the seismic QBP is not observed in the
surface activity indices, where mid-term variations are found only time to time
and mainly over periods of high activity. This feature together with the
latitudinal dependence provides more evidences in favor of a mechanism almost
independent and different from the one that brings up to the surface the active
regions. Therefore, these findings can be used to provide more constraints on
dynamo models that consider a further cyclic component on top of the 11-year
cycle.Comment: 9 pages, 9 Figures, 2 Tables Accepted for publication in A&
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