- 宇宙科学研究所報告. 特集 (ISSN:02859920)
- vol.4, pp.93-105, 1982-08
Direct photographs of the solar granulation near the limb were obtained with a 30cm balloon-borne telescope. The observed position on the solar disk was at cosθ=0.7,where θ is the angle between the observer and the normal to the solar surface and the wavelength used was 545nm with a pass band of 40nm. Total half-width (FWHM) of the autocorrelation function of the contrast of the granulation was found to be 780km and 660km in radial and tangential direction to the solar limb, respectively. Although the latter value agrees with the older determination at the disk center, the distance, 2000km, to the minimum value of the auto-correlation function was much larger than those obtained by Leighton at the disk center. Two dimensional power spectrum was obtained and after corrections due to noise spectrum and finite resolution of the optical system, the root-mean-square brightness fluctuation of the granulation was found to be 7.0-7.9%. It is to be noted that the modulation transfer function of the optical system was determined at the partial eclipse of July, 30,1981. Two dimensional power spectrum per unit frequency area (arcsec^2) was fonund to be proportional to exp (-1.9f) where f is the frequency (cycles/arcsec). Further the autocorrelation function as determined from the earlier balloon flight with the use of a 10cm telescope showed a positive maximum around 24∿45Mm, which roughly coincides with the size of the supergranulation.