Measurements Of Solar Oblateness Research Articles

Revisiting the Solar Oblateness: Is Relevant Astrophysics Possible?

The measurement of solar oblateness has a rich history extending well back into the past. Until recently, its estimate has been actively disputed, as has its temporal dependence. Recent accurate observations of the solar shape gave cause for doubt, and so far only balloon flights or satellite experiments, such as those onboard SDO, seem to achieve the required sensitivity to measure the expected small deviations from sphericity. A shrinking or an expanding shape is ultimately linked to solar activity (likely not homologously with its change), as gravitational or magnetic fields, which are existing mechanisms for storing energy during a solar cycle, lead to distinct perturbations in the equilibrium solar-structure and changes in the diameter. It follows that a sensitive determination of the solar radius fluctuations might give information about the origin of the solar cycle. In periods of higher activity, the outer photospheric shape seems to become aspheric under the influence of higher-order multipole moments of the Sun, resulting both from the centrifugal force and the core rotation. An accurate determination of the shape of the Sun is thus one of the ways that we have now for peering into its interior, learning empirically about flows and motions there that would otherwise only be guessed at from theoretical considerations, developing more precise inferences, and ultimately building possible alternative gravitational theories.

A brief history of the solar oblateness. A review

We hereby present a review on solar oblateness measurements. By emphasizing historical data, we illustrate how the discordance between experimental results can lead to substantial improvements in the building of new technical apparatus as well as to the emergence of new ideas to develop new theories. We stress out the need to get accurate data from space to enhance our knowledge of the solar core in order to develop more precise ephemerids and ultimately build possible new gravitational theories.

Towards an Analysis of Scientific Observation: The Externality and Evidential Significance of Observational Reports in Physics

In this paper a new schema for the analysis of scientific observation is proposed. The concepts of `externality' and `evidential' context of observational reports are introduced. The degree of externality of reports is shown to be related to the specificity of the evidential context. Attention is drawn to how the new concepts differ from traditional issues raised by the problem of the theory-ladenness of observations. The analysis is illustrated by reference to the detection of solar neutrinos and measurements of solar oblateness. Detailed studies of these cases reveal how the externality and evidential context shifts during the course of observational disputes. Some of the consequences of the new schema for the analysis of scientific language, access to experimental data, and black-box instrumentation are developed.

Is the Sun an oblique magnetic rotator?

The recent observation1 of rotational splitting of the non-radial p modes of l = 1 and l = 2 (with it n∼20) of the 5-min global oscillation of the Sun was interpreted in terms of rotational splitting associated with a rapid rotation of the solar interior. The precise value deduced for the angular velocity Ω of the interior depends on the assumed variation of Ω with depth and on the weighting function. Thus with a weighting function2 of the form &Ω=∫Ω(r)/V(r) dr ∫dr/V(r) (1) where V(r) is the local velocity of sound at radius r, one obtains values of Ωcore/Ωsurface ranging from 2 to 9 as the radius at which Ω, assumed to be constant for smaller r, ranges from 0.6 to 0.15 of the solar radius. Such a weighting function proportional to the time the wave spends at any particular radius seems very plausible for the effect of any parameter, be it angular velocity or magnetic field, on the propagation of nearly plane waves as they bounce between the centre and the surface. Here I attempt to correlate the size of the observed rotational splitting with the enigmatic 12.2-day variation in the measurement of solar oblateness discovered by Dicke3 previously4 and to interpret the observed near equality of the amplitudes of the m- components of the l = 1 and l = 2 rotationally split modes. This leads to the first empirical evidence that an asymmetric magnetic rotator with megagauss magnetic fields exists in the interior of the Sun. It also suggests that the magnetic energy of young stars is a sizeable fraction of their gravitational energy.

Regression of the Node of the Orbit of Mercury due to a Solar Quadrupole Moment

view Abstract Citations (5) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Regression of the Node of the Orbit of Mercury due to a Solar Quadrupole Moment O'Connell, R. F. Abstract Assuming that the solar quadrupole moment is given by the value deduced by Dicke and Goldenberg from their solar oblateness measurements, Audretsch, Dehnen, and Hönl recently concluded that the node of the orbit of Mercury regresses at a rate of 3'~4 per century. However, this rate is with respect to the Sun's equatorial system. Now, the observations of all planetary orbits are described with respect to the equinox and ecliptic of a given epoch, and we show that, with respect to this system, the rate of re- gression is only O'~27 per century, which is actually smaller than the experimental error of 1" per century Publication: The Astrophysical Journal Pub Date: April 1968 DOI: 10.1086/180167 Bibcode: 1968ApJ...152L..11O full text sources ADS |