Abstract
view Abstract Citations (83) References (54) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Oblateness of the Sun Dicke, R. H. ; Goldenberg, H. Mark Abstract The solar oblateness observations of 1966 are analyzed. Included are measures of the vertical and diagonal components of the oblateness. These components represent the fractional contractions of the solar disk along the north-south and the northeast-southwest diameters, respectively. Also included are the annular-ring measures of the equatorial brightening of the solar disk. These "brightness data" are obtained by scanning a thin annular aperture centered on the solar disk. The daily values of the diagonal component of the oblateness are correlated with the observatory temperature and humidity and with atmospheric transparency to test for a correlated atmospheric bias of the results. Seasonal averages of the hourly averages of the data provide measures of (and corrections for) the seeing distortions of the solar image. The correction of the diagonal component for seeing effects is zero. Functions derived from distributions about the limb of faculae, sunspots, magnetic fields, and prorninences are correlated with the diagonal component of the oblateness. Only the facular signal is important. The facular contribution is greatest when the largest amount of photosphere is exposed at the limb. Mter subtracting the facular contribution to the signal, the residual oblateness is independent of the amount of photosphere exposed. Averaged over all three limb exposures, only 14 percent of the oblateness signal is due to faculae. Correlation coefficients of the facular signal with the "brightness data" and with the vertical component of the oblateness are also computed. The "brightness data" show no equatorial brightening over and above that due to faculae. The 23d.67 periodicity of the solar oblateness is studied. The periodic autocorrelation function of the oblateness fluctuation, the periodic fluctuation component in the data, and the cross-correlation function of the data with the periodic component are evaluated. The periodic fluctuation component exhibits sharp positive peaks separated by 12 days. The values for the oblateness obtained from the diagonal and vertical components are consistent with each other and yield a mean value of ArIr = 4.31 + 0.34 x 10- . The solar quadrupole moment consistent with this value, j = 2.47 + 0.23 x 10 - 5, implies a correction of 2 .98 + per century to the `classical excess motion of Mercury's perihelion. Subject headings: faculae, solar - interiors, solar - Mercury - rotation, solar Publication: The Astrophysical Journal Supplement Series Pub Date: March 1974 DOI: 10.1086/190292 Bibcode: 1974ApJS...27..131D full text sources ADS |
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