Solar oscillations: full disk observations from the geographic South Pole

Grec, G.; Fossat, E.; Pomerantz, M. A.

doi:10.1038/288541a0

Cited by 268 publications

(97 citation statements)

References 14 publications

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“…This was immediately identified, after being first resolved by the South Pole data set in 1980 (Grec et al 1980(Grec et al , 1983, as a parameter probing the solar core because it measures a difference of two kernels that are essentially identical in the upper layers and different in the deepest layers. Unfortunately, it requires more than two days of measurement to be resolved, so that only g modes with periods longer than these two days could be tracked.…”

Section: Looking Differently and Elsewherementioning

confidence: 99%

Asymptotic g modes: Evidence for a rapid rotation of the solar core

Fossat

Boumier

Corbard

et al. 2017

A&A

114

212

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Context. Over the past 40 years, helioseismology has been enormously successful in the study of the solar interior. A shortcoming has been the lack of a convincing detection of the solar g modes, which are oscillations driven by gravity and are hidden in the deepest part of the solar body -its hydrogen-burning core. The detection of g modes is expected to dramatically improve our ability to model this core, the rotational characteristics of which have, until now, remained unknown. Aims. We present the identification of very low frequency g modes in the asymptotic regime and two important parameters that have long been waited for: the core rotation rate, and the asymptotic equidistant period spacing of these g modes. Methods. The GOLF instrument on board the SOHO space observatory has provided two decades of full-disk helioseismic data. The search for g modes in GOLF measurements has been extremely difficult because of solar and instrumental noise. In the present study, the p modes of the GOLF signal are analyzed differently: we search for possible collective frequency modulations that are produced by periodic changes in the deep solar structure. Such modulations provide access to only very low frequency g modes, thus allowing statistical methods to take advantage of their asymptotic properties. Results. For oscillatory periods in the range between 9 and nearly 48 hours, almost 100 g modes of spherical harmonic degree 1 and more than 100 g modes of degree 2 are predicted. They are not observed individually, but when combined, they unambiguously provide their asymptotic period equidistance and rotational splittings, in excellent agreement with the requirements of the asymptotic approximations. When the period equidistance has been measured, all of the individual frequencies of each mode can be determined. Previously, p-mode helioseismology allowed the g-mode period equidistance parameter P 0 to be bracketed inside a narrow range, between approximately 34 and 35 minutes. Here, P 0 is measured to be 34 min 01 s, with a 1 s uncertainty. The previously unknown g-mode splittings have now been measured from a non-synodic reference with very high accuracy, and they imply a mean weighted rotation of 1277 ± 10 nHz (9-day period) of their kernels, resulting in a rapid rotation frequency of 1644 ± 23 nHz (period of one week) of the solar core itself, which is a factor 3.8 ± 0.1 faster than the rotation of the radiative envelope. Conclusions. The g modes are known to be the keys to a better understanding of the structure and dynamics of the solar core. Their detection with these precise parameters will certainly stimulate a new era of research in this field.

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Section: Looking Differently and Elsewherementioning

confidence: 99%

Asymptotic g modes: Evidence for a rapid rotation of the solar core

Fossat

Boumier

Corbard

et al. 2017

A&A

114

212

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“…Observations by Claverie et al (1979) and by Grec, Fossat, and Pomerantz (1980), which utilized the integrated light from the entire solar disk, showed that the oscillations are globally coherent. The modes observed by these techniques provide the most important information currently available for the study of the deep solar interior since they penetrate most deeply toward the solar center.…”

Section: Helioseismologymentioning

confidence: 99%

The Standard Solar Model

Bahcall¹

1990

International Astronomical Union Colloquium

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ABSTRACT. The main features of standard solar models, the logic of the calculations, and some of the important results concerning solar neutrinos experiments are given. The input parameters that cause the greatest uncertainties in the calculated neutrino fluxes are the nuclear rection rates, the chemical abundances, the radiative opacity, and the equation of state. This article is based, with permission of the publisher, on Chapters 1 and 4 of Neutrino Astrophysics by J. N. Bahcall, Cambridge University Press (1989). IntroductionThe Sun is an astronomical laboratory. Because of its proximity to the Earth, we are able to obtain information about the Sun that is not accessible for other stars. We can determine precise values for the solar mass, radius, geometric shape, photon spectrum, total luminosity, surface chemical composition, and age. In addition, astronomers have measured accurate frequencies for thousands of acoustic oscillation modes that are observed at the solar surface. These frequencies contain information about the solar interior. We are beginning to measure the spectrum of neutrinos produced by nuclear reactions in the solar interior. The geological records, the planets, comets, and meteorites, provide information about the past history of the Sun. Taken together, this treasure of experimental information provides a unique opportunity to test theories of stellar structure and evolution. For two decades, the only operating solar neutrino experiment yielded results in conflict with the most accurate theoretical calculations. This conflict between theory and observation, which has recently been confirmed by a new experiment, is known as the solar neutrino problem. This problem can be stated simply. Both the theoretical and the observational results are expressed in terms of the solar neutrino unit, SNU, which is the product of a characteristic calculated solar neutrino flux (units: c m -2 s _1 ) times a theoretical cross section for neutrino absorption (unit: cm 2 ). A SNU has, therefore, the units of events per target atom per second and is chosen for convenience equal to 1 0 _ 3 6 s -1 .The predicted rate for capturing solar neutrinos in a 37 C1 target is Predicted rate = (7.9 ± 2.6) SNU,where the indicated uncertainty represents the total theoretical range including three standard deviation (3

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“…This theoretical developments were confirmed by the detection of the p-mode power spectrum of the 5 minutes oscillations reported by Claverie et al (1979) confirming the existence of global modes. These observations were then improved by Grec et al (1980) thanks to the measurements obtained during 120 continuous hours from the South Pole, which sensibly improved the overall quality of the spectrum by reducing the daily aliases. The helioseismology, as we know it today was officially born.…”

Section: Acoustic Modesmentioning

confidence: 99%

“…In such way, modes that are equally spaced by this quantity are aligned forming vertical ridges. It was originally introduced in helioseismology by Grec et al (1980) to correctly identify the modes of the power spectrum of the Sun measured from the South Pole. Nowadays, this type of diagram is commonly used in asteroseismology to properly tag the degree and the order of the modes.…”

Section: Theéchelle Diagrammentioning

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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Solar oscillations: full disk observations from the geographic South Pole

Cited by 268 publications

References 14 publications

Asymptotic g modes: Evidence for a rapid rotation of the solar core

Asymptotic g modes: Evidence for a rapid rotation of the solar core

The Standard Solar Model

Observational techniques to measure solar and stellar oscillations

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