Rotation of the solar core from BiSON and LOWL frequency observations

Chaplin, W. J.; Christensen‐Dalsgaard, J.; Elsworth, Y.; Howe, R.; Isaak, G. R.; Larsen, Ryan Godsk; New, R.; Schou, J.; Thompson, M. J.; Tomczyk, S.

doi:10.1046/j.1365-8711.1999.02691.x

Cited by 78 publications

(65 citation statements)

References 19 publications

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“…The surface velocity of both AGSR and AGSM is about 2 km s −1 . Efficient transport of angular momentum flattens the angular velocity profile of AGSM between about 0.3 and 0.7 R e (see Figure 5), which is consistent with theseismically inferred result (Chaplin et al 1999a) and is compatible with the first observation of gravity modes (see Figures 2 and 4 of AGSR. The magnetic energy is mainly stored in the radiative region (see Figure 5).…”

Section: Rotating Model Including the Effects Of Magnetic Fieldssupporting

confidence: 89%

Solar Models With New Low metal Abundances

Yang

2016

ApJ

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In the past decade, the photospheric abundances of the Sun had been revised several times by many observers. The standard solar models constructed with the new low-metal abundances disagree with helioseismic results and detected neutrino fluxes. The solar model problem haspuzzled somestellar physicists for more than 10years. Rotation, enhanced diffusion, convection overshoot, and magnetic fields are used to reconcile the new abundances with helioseismology. The too lowhelium subsurface abundance in enhanced diffusion models can be improved by the mixing caused by rotation and magnetic fields. The problem of the depth of the convective zone in rotating models can be resolved by convection overshoot. Consequently, the Asplund-Grevesse-Sauval rotation model including overshooting (AGSR) reproduces the seismically inferred sound-speed and density profilesand the convection zone depth as well as the Grevesse & Sauval model computed before. But this model fails to reproduce the surface helium abundance, which is 0.2393 (2.6σ away from the seismic value), and neutrino fluxes. The magnetic model called AGSM keeps the agreement of the AGSR and improves the prediction of the surface helium abundance. The observed separation ratios r 02 and r 13 are reasonably reproduced by AGSM. Moreover, neutrino fluxes calculated by this model are not far from the detected neutrino fluxes and the predictions of previous works.

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Section: Rotating Model Including the Effects Of Magnetic Fieldssupporting

confidence: 89%

Solar Models With New Low metal Abundances

Yang

2016

ApJ

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“…15). The solar rotational profile is known in great detail for only those regions probed by pressure-dominated modes [16][17][18] . In contrast to these modes in the wings of the dipole forest, only 30% of the splitting of the centre mode originates from the central region of the star, whereas the outer third by mass of the star contributes 50% of the frequency splitting.…”

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confidence: 99%

Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes

Beck

Montalbán

Kallinger

et al. 2011

Nature

488

544

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When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant. Convection takes place over much of the star's radius. Conservation of angular momentum requires that the cores of these stars rotate faster than their envelopes; indirect evidence supports this 1,2 . Information about the angular-momentum distribution is inaccessible to direct observations, but it can be extracted from the effect of rotation on oscillation modes that probe the stellar interior. Here we report an increasing rotation rate from the surface of the star to the stellar core in the interiors of red giants, obtained using the rotational frequency splitting of recently detected 'mixed modes' 3,4 . By comparison with theoretical stellar models, we conclude that the core must rotate at least ten times faster than the surface. This observational result confirms the theoretical prediction of a steep gradient in the rotation profile towards the deep stellar interior 1,5,6 .The asteroseismic approach to studying stellar interiors exploits information from oscillation modes of different radial order n and angular degree l, which propagate in cavities extending at different depths 7 . Stellar rotation lifts the degeneracy of non-radial modes, producing a multiplet of (2l 1 1) frequency peaks in the power spectrum for each mode. The frequency separation between two mode components of a multiplet is related to the angular velocity and to the properties of the mode in its propagation region. More information on the exploitation of rotational splitting of modes may be found in the Supplementary Information. An important new tool comes from mixed modes that were recently identified in red giants 3,4 . Stochastically excited solar-like oscillations in evolved G and K giant stars 8 have been well studied in terms of theory [9][10][11][12] , and the main results are consistent with recent observations from space-based photometry 13,14 . Whereas pressure modes are completely trapped in the outer acoustic cavity, mixed modes also probe the central regions and carry additional information from the core region, which is probed by gravity modes. Mixed dipole modes (l 5 1) appear in the Fourier power spectrum as dense clusters of modes around those that are best trapped in the acoustic cavity. These clusters, the components of which contain varying amounts of influence from pressure and gravity modes, are referred to as 'dipole forests'.We present the Fourier spectra of the brightness variations of stars KIC 8366239 (Fig. 1a), KIC 5356201 ( Supplementary Fig. 3a) and KIC 12008916 ( Supplementary Fig. 5a), derived from observations with the Kepler spacecraft. The three spectra show split modes, the spherical degree of which we identify as l 5 1. These detected multiplets cannot have been caused by finite mode lifetime effects from mode damping, because that would not lead to a consistent multiplet appearance over several orders such as that shown in Fig. 1. ...

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“…Thompson et al 1996) and the radiative zone (e.g. Chaplin et al 1999a;Couvidat et al 2003;Eff-Darwich et al 2008;Eff-Darwich & Korzennik 2013;Elsworth et al 1995;García et al 2004García et al , 2008c or the conditions and properties of the solar core (e.g. Appourchaux et al 2010;Basu et al 1997Basu et al , 2009García et al 2007García et al , 2008aTurck-Chièze et al 2001, 2004 are some wellknown examples.…”

Section: Helio and Asteroseismologymentioning

confidence: 99%

Observational techniques to measure solar and stellar oscillations

García

2015

EAS Publications Series

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Abstract.As said by Sir A. Eddington in 1925: "Our telescopes may probe farther and farther into the depths of space. At first sight it would seem that the deep interior of the sun and stars is less accessible to scientific investigation than any other region of the universe. What appliance can pierce through the outer layers of a star and test the conditions within?" Eddington (1926). Nowadays, asteroseismology has proven its ability to pierce below stellar photospheres and allow us to "see" inside the interior of thousands of stars down to the stellar cores, answering the question asked by Eddington ninety years ago. In this chapter we review the general properties of the spectral analysis which is the base of any asteroseismic investigation. After describing the stellar power spectrum, we will describe in details the characterization of the modal spectrum. This chapter will end by a brief description of the instrumentation in both helio and asteroseismology.

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Rotation of the solar core from BiSON and LOWL frequency observations

Cited by 78 publications

References 19 publications

Solar Models With New Low metal Abundances

Solar Models With New Low metal Abundances

Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes

Observational techniques to measure solar and stellar oscillations

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