view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Solar granulation. The frequency spectrum of photo spheric brightness at long spatial wave lengths. Wlérick, Gérard Abstract A very good photograph of solar granulation taken by Dr. W. A. Miller at Rocky Point, Long Island, N. Y., has been analyzed. The aperture of the telescope was 4.5 inches and the plate Kodak 548 GH. As no colored filter was used, the plate was impressed by radiations from the interval 3600-5650A. With the microphotometer of the High Altitude Observatory tracings were made along two linear paths whose total length corresponds to 1,140,000 km on the sun. The statistical analysis was similar to that made by Frenkiel and Schwarzschild (1955) and by Uberoi (1955) for solar granulation photographs taken at Mount Wilson with a ~-inch aperture in a narr9w wavelength interval centered around 58oo A. It consisted of the computation of the autocorrelation function of brightness, of the one-dimensional frequency spectrum and of the two-dimensional frequency spectrum. A correction was applied for the finite resolution of the telescope due to diffraction and chromatic aberration. The results indicate that in the range of spatial wave lengths from 87,000 km to 3140 km, wave numbers from 7.2 X 10-I km-0 to 2 X io-3 km-0, the two-dimensional frequency spectrum P (k) is of the low frequency type, i.e., the average energy per unit frequency decreases with frequency. The results thus differ from those of Frenkiel and Schwarzschild and of Uberoi who found with Mount Wilson photographs that the frequency spectrum was nearly constant in the range from 30,000 to 2000 km, wave numbers from 2 X io-4 km-0 to 3 10-I km-0. The difference implies that more energy resides in larger scale granular structure for the shorter wave-length images used by Miller and indicates the importance of homogeneous granule studies simultaneously at several colors. The help of Miss Sabine Hirsch for the computation is gratefully acknowledged. This work was supported by the Radio Corporation of America and the Geophysics Research Directorate, Air Force Cambridge Research Center. Frenkiel, F. N. and Schwarzschild, M. 1955, Ap. J. 121, 216. Uberoi, M. S. 1955, Ap. J. 122, 466. High Altitude Observatory, Boulder, Colo. Publication: The Astronomical Journal Pub Date: 1957 DOI: 10.1086/107592 Bibcode: 1957AJ.....62Q..39W full text sources ADS |