The Double Reversal in the Cores of the Fraunhofer H and K Lines.

Abstract

view Abstract Citations (40) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Double Reversal in the Cores of the Fraunhofer H and K Lines. Goldberg, Leo ; Mohler, O. C. ; Müller, Edith A. Abstract Observations are presented of the profiles of the central doubly reversed cores of the H and K lines of Ca ii in the Fraunhofer spectrum. The profiles were obtained photoelectrically with the vacuum spectograph of the McMath-Hulbert Observatory at five different points on the solar disk from M = 1.0 to = 0.2. At the center of the disk the central intensities of H and K are 2.95 and 2.36 per cent, respectively, in terms of the neighboring continuous spectrum near X 4000. At = 0.2 the central intensities are 2.41 and 2.01 per cent for H and K, respectively, also with reference to the continuum at X 4000 at the center of the disk. The relative intensity ratio H: K is found to be constant in the inner absorption core and nearly the same for all values of . This suggests that the logarithm of the source function varies linearly with the logarithm of Nh, the number of Ca ii atoms per square centimeter above height, h, in the chromosphere. The Doppler widths were derived by two methods, namely, (1) by an intercomparison method which is independent of the source functiop and (2) by using the depth-dependence of the source function and the shapes of the profiles. The Doppler widths thus found increase from 0.063 A at = 1.0 to 0.110 A at = 0.2. The derived Doppler widths and source function are employed to calculate the profiles of the inner cores of H and K. Extremely good agreement is found between the calculated and the observed central cores at all five values of . The variation in the Doppler widths from center to limb is discussed, and it is concluded that the widening of the profiles to the limb is caused by an increase in turbulence with height, combined with anisotropy. The comparison of the Doppler widths derived for Ca ii with results previously obtained for the X 10830 line of He I supports the hypothesis that the chromosphere is heterogeneous and is composed of regions of quite different physical properties. Publication: The Astrophysical Journal Pub Date: January 1959 DOI: 10.1086/146600 Bibcode: 1959ApJ...129..119G full text sources ADS |