Solar Oblateness, Excess Brightness, and Relativity

Hill, H. A.; Clayton, Paul D.; Pätz, Daniel; Healy, A. W.; Stebbins, R. T.; Oleson, James R.; Zanoni, C. A.

doi:10.1103/physrevlett.33.1497

Cited by 52 publications

(9 citation statements)

References 11 publications

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“…Hill, a former colleague of Dicke who had helped build the instrument with which the 1964 observations were made (Dicke, 1964), and collaborators, also attempted to measure the solar oblateness, using an instrument, SCLERA [Santa Catalina Observatory for Experimental Relativity by Astrometry], which was later to play a role in the early days of helioseismology. This measurement, carried out in 1973, (Hill and Stebbins, 1975), found a 9.6 × 10 −6 value for the oblateness, much smaller than that of Dicke and Goldenberg (1967b); Hill et al (1974) also pointed out a time-varying difference between the brightness of the solar limb and poles that might account for the anomalously high oblateness measurement. Ulrich and Hawkins (1981a,b) made an early attempt to deduce what the J 2 and J 4 terms should be based on a simple differential rotation profile deduced from surface measurements, obtaining predicted values of between 1 and 1.5 × 10 −7 for J 2 and between 2 and 5 × 10 −9 for J 4 depending on the size of the convective envelope.…”

Section: The Oblateness Controversymentioning

confidence: 78%

Solar Interior Rotation and its Variation

Howe

2009

Living Rev. Solar Phys.

370

246

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This article surveys the development of observational understanding of the interior rotation of the Sun and its temporal variation over approximately forty years, starting with the 1960s attempts to determine the solar core rotation from oblateness and proceeding through the development of helioseismology to the detailed modern picture of the internal rotation deduced from continuous helioseismic observations during solar cycle 23. After introducing some basic helioseismic concepts, it covers, in turn, the rotation of the core and radiative interior, the "tachocline" shear layer at the base of the convection zone, the differential rotation in the convection zone, the near-surface shear, the pattern of migrating zonal flows known as the torsional oscillation, and the possible temporal variations at the bottom of the convection zone. For each area, the article also briefly explores the relationship between observations and models.

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Section: The Oblateness Controversymentioning

confidence: 78%

Solar Interior Rotation and its Variation

Howe

2009

Living Rev. Solar Phys.

370

246

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“…The solar quadrupole moment also plays a role in general relativity (Hill et al 1974) and in celestial mechanics. The relativistic precession of the perihelion of planets is a known phenomenon (Pireaux & Rozelot 2003), ∼43 arcsec per century in the case of Mercury.…”

Section: Relativistic Celestial Mechanicsmentioning

confidence: 99%

Probing the Solar Surface: The Oblateness and Astrophysical Consequences

Rozelot

Damiani

Pireaux

2009

ApJ

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Based on historical records, the Sun's dimensions are temporally dependent. Until the recent past, varying dimensions were keenly disputed. Recent accurate observations have removed the doubt, whether from direct limb observations or from helioseismology f-modes analysis. A shrinking or an expanding shape is ultimately linked to solar activity, as even a small variation in the solar radius causes variations in gravitational energy. Based on accurate space-and ground-based observations, we will argue that the oblateness of the Sun is time dependent. Indeed, considering the first two shape coefficients, we can interpret such a temporal variation as a change in the relative importance of the hexadecapolar term, i.e., at the time of high activity, only the dipolar moment c 2 has a significant effect, but at the time of low activity, c 4 is predominant; this results in a decrease of the total value of the oblateness. The combination of the two terms leads to a solar oblateness varying along with solar activity. More studies are needed to get accurate measurements from space, which will provide us with the unique opportunity to study detailed changes of global solar properties.

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“…All such models must eventually satisfy several general observational constraints. Among these are (1) differential rotation; (2) practically uniform radiant energy output, i.e., variation with latitude less than a few parts in 103 [Caccin et al, 1970;Altrock and Canfield, 1972;Noyes et al, 1973;Peraiah, 1973;Hill et al, 1974]; and (3) a hydromagnetic dynamo action that provides the basic observed characteristics of the activity cycle--or at least a model that does not interfere with some other mechanism that does. cock, 1961;Krause and R/idler, 1971;Roberts and Stix, 1972;Stix, 1976; Yoshimura, 1978] can obtain reasonable agreement with observed properties of the cycle only with a rotation rate that increases inward at least in the upper.convection zone.…”

Section: Theorymentioning

confidence: 99%

The rotation of the Sun

Howard¹

1978

Reviews of Geophysics

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Observations of solar rotation are reviewed. There are two basic methods of determining the rotation of the sun. One is to measure the daily or monthly positions of tracers on the surface or in the corona, and the other is to measure line‐of‐sight velocities with the Doppler effect in spectrum lines. The results of a number of investigations involving both methods are compared. The experimental and interpretational problems associated with observational determinations of solar rotation are reviewed and compared. The theoretical situation in this field is reviewed, including the significance of different rotation rates for surface magnetic features and the solar plasma. The rotation of the solar interior is discussed in terms of both model calculations and recent p mode oscillation rotation rates, which reflect the interior rotation.

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Solar Oblateness, Excess Brightness, and Relativity

Cited by 52 publications

References 11 publications

Solar Interior Rotation and its Variation

Solar Interior Rotation and its Variation

Probing the Solar Surface: The Oblateness and Astrophysical Consequences

The rotation of the Sun

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