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Godier, S.; Rozelot, Jean-Pierre

doi:10.1023/a:1010354901960

Cited by 38 publications

(32 citation statements)

References 7 publications

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“…Observations provide only upper limits on the strength of the magnetic field in the radiation zone of the Sun (see, e.g., Godier & Rozelot 2000;Antia et al 2000). For other stars estimates are much less certain and only theoretical upper limits can be derived.…”

Section: Introductionmentioning

confidence: 99%

Rotation and Stability of the Toroidal Magnetic Field in Stellar Radiation Zones

Bonanno

Урпин

2013

ApJ

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The stability of the magnetic field in radiation zones is of crucial importance for mixing and angular momentum transport in the stellar interior. We consider the stability properties of stars containing a predominant toroidal field in spherical geometry by means of a linear stability in the Boussinesq approximation taking into account the effect of thermal conductivity. We calculate the growth rate of instability and analyze in detail the effects of stable stratification and heat transport. We argue that the stabilizing influence of gravity can never entirely suppress the instability caused by electric currents in radiation zones. However, the stable stratification can essentially decrease the growth rate of instability.

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Section: Introductionmentioning

confidence: 99%

Rotation and Stability of the Toroidal Magnetic Field in Stellar Radiation Zones

Bonanno

Урпин

2013

ApJ

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“…When the measurements are grouped by classes of latitude of at least 5 to 10 degrees, the results are more in accordance (Godier & Rozelot 1999). This can be explained, as part of the radius variation is due to solar deformation, linked on the one hand with the royal zones where the existence of spots diminishes the measured brightness, and as a consequence the measured radius; and on the other hand, with the high-latitude activity zones where the presence of faculae have the inverse effect (Pecker 1996).…”

Section: Comparison With Other Measurements Of the Solar Radiusmentioning

confidence: 70%

“…Summary of total solar irradiance measurements total irradiance, which is not explained by the effect of sunspots, faculae, and the magnetic network, is a difficult problem since global effects may also produce variations in total irradiance. It has been shown that changes in the differential rotation in the interior of the Sun, the solar dynamo magnetic field near the base of the convective zone (Kuhn 1996, photospheric temperature changes (Kuhn et al 1988), large scale missing flows or large scale convective cells (Ribes et al 1985;Fox & Sofia 1994) and/or radius changes (Delache et al 1985;Ulrich & Bertello 1995;Kuhn et al 1985Kuhn et al , 1988Godier & Rozelot 2000) may also contribute to irradiance variations. Therefore, simultaneous studies of total irradiance and solar global parameters are essential to better understand the underlying physical mechanism of irradiance changes and to predict solar-induced climate changes.…”

Section: Description Of the Total Irradiance Measurementsmentioning

confidence: 99%

On the relation between total irradiance and radius variations

Pap

Rozelot²,

Godier³

et al. 2001

A&A

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Abstract. We use Singular Spectrum Analysis (SSA) to analyze total solar irradiance variations and CERGA radius measurements. Total solar irradiance has been monitored from space for more than two decades, whilst ground-based radius measurements are available as a coherent time series from 1975. We compare these indicators to try to understand the origin of energy production inside the Sun. One of the main objectives was to assess the reality of the observed variations of the Sun's radius by distinguishing the signal from the noise. Two approaches were used: one using SSA on ground-based data averaged over 90 days, in order to smooth the signal (especially over periods when no data were obtained, mainly in winter time); the second repeats the analysis on individual measurements corrected by reporting data to the zenith. As expected, the level of noise is higher in the first case and the reconstructed noise level, which is large, indicates the difficulty in ascertaining the solar origin in the apparent variability of the solar radius. It is shown from the reconstructed components that the main variation in amplitude (over 930 days) is pronounced during the first part of the measurements and seems to disappear after 1988. There is also a variation with a periodicity of 1380 days, of lower amplitude than that of the shorter component. In both cases, these variations disappear during the rising portion of cycle 23. The first reconstructed component shows that total irradiance varies in parallel with the solar cycle, being higher during maximum activity conditions. The reconstructed radius trend indicates that the solar radius was higher during the minimum of solar cycle 21, but its decrease with the rising activity of cycle 23 is less obvious. The observed value of the solar radius increased by about 0.11 arcsec from the maximum of cycle 21 to the minimum between cycles 21 and 22. Most importantly, we report a long-term radius variation which increased from the maximum of cycle 21 to minimum by about 0.015%, while a smaller decrease (around 0.01%) is seen from the minimum of cycle 21 to the maximum of cycle 22. This study indicates need for measurements of the degree of the radius changes taken from space, together with total irradiance measurements to establish the phase relation between these two quantities.

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“…From the complete study of a differentially rotating Sun, [7] concluded that the exact shape critically depends both on the rotation law from the subsurface to the tachocline. As before, we have named the study zone extending in the layer 0.703R -0.723R as LCR, which includes the 10 4 km deep overshoot layer [8].…”

Section: Introductionmentioning

confidence: 99%

On the modelling of rotational effects in the lower convective region of the sun

Çavuş¹,

Karafistan²

2010

Braz. J. Phys.

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The purpose of this work is to study effects of differential rotation in the lower convective region of the Sun. Similar to MHD case; the governing equations are separated in variables, allowing numerical integration in this layer. This algorithm facilitates solutions of more complicated systems, with less computing time. Two different known rotation profiles are used in order to fit the model. The fitting procedure is accomplished by making use of sphericity and density shape parameters related to the rotation profiles. It is also shown that the most important feature of rotation is to break the spherical symmetric distribution of density in this layer. As in the MHD effects found before, differential rotation changes considerably the density of the reference model for both cases.

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Untitled

Cited by 38 publications

References 7 publications

Rotation and Stability of the Toroidal Magnetic Field in Stellar Radiation Zones

Rotation and Stability of the Toroidal Magnetic Field in Stellar Radiation Zones

On the relation between total irradiance and radius variations

On the modelling of rotational effects in the lower convective region of the sun

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