Some Results from a Study of the Atomic Lines in the Sun-Spot Spectrum

Abstract

view Abstract Citations (4) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Some Results from a Study of the Atomic Lines in the Sun-Spot Spectrum Moore, Charlotte E. Abstract A detailed study of the atomic lines in the sun-spot spectrum has resulted in a deter- mination of the effective temperature of sun-spots and the pressure and amount of material above them. Intensities for 6312 lines of atomic origin in the spot spectrum have been estimated on the Rowland scale on original negatives and on prints made from them. The plates were those taken with the 150-foot tower telescope and 75-foot spectrograph for the Mount Wilson map of the spot spectrum. The third order was used from X39oo to X 5400; the second order from X 5400 to X óooo. The spectrum of the disk appears on each side of the spot spectrum. The use of a quarter-wave plate and Nicol prism gives the lines subject to Zeeman effect a dentate appearance in the spectrum of the spot, which makes it possible to select the atomic lines. Intensities estimated from the prints agree systematically with those from the plates. The identifications of lines in the solar spectrum from X 2975 to X 6635 and in the spot spectrum from X 3894 to X 6635 have been revised and extended. Lines of Lu~ have been identified for the first time. The principal criteria employed have been labora- tory wave-lengths and intensities, the multiplet relations and excitation potentials, which are now available for almost all elements except the rare earths, and the behavior of the lines in the spectrum of `y Cygni, a giant star of class F8. Nine hundred and thirty-six faint solar lines not previously identified and 21 spot lines have been recog- nized as faint members of mattiplets not yet observed in the laboratory, but accurately predictable. Of these, 437 are due to Fe, 122 to Cr, 89 to Ni, 73 to Cr~, 67 to Ti, 50 to F&, 43 to Ti+, 21 to Co, 20 to Zr+, 12 to V, 9 to V~, 7 to Sc+, and 7 to Mn. Three hun- dred and ninety-six new atomic lines which appear only in the spot spectrum have been measured and 193 identified. A quantitative study of the composition of the atmosphere above sun-spots has been based on the calibration of the Rowland intensity scale. This gives a quantity Y, which is the logarithm of the ratio of the number of atoms producing a line in the spot spec- trum to that effective in the formation of the same line in the solar spectrum. From thermodynìamic theory Y = Y0+SE~, where V0 is the logarithm of the ratio of the num- bers of neutral atoms above equal areas of the photospheres of spot and disk, E~ the excitation potential, and S=5o4o (i/T- i/T'). Tand T' are the effective temperatures of disk and spot, respectively. For enhanced lines, Y0 must be replaced by Y1, the corre- sponding quantity for ionized atoms. The observed data from 6 elements give a weighted mean value of S equal to -0.190 ± 0.010. Taking T= 57400 K, T' = 47200 ± 4Q0 K, where the probable error is a measure of the accordance of the observations. From the observed values of V0 and V1 and the Saha equation as modified by Pannekoek and Fowler, the ratio of the electron pressures P~ (spot) and Fe (disk) can be found. Eight elements have a sufficient number of arc and spark lines present in both solar and spot spectra to be used. The weighted mean value of log (P~/Pe) iS -0.22 ± 0.07, i.e., the electron pressure over the spot is o.6o ± 0.10 times that over the disk. Russell has defined the "level of ionization" as the ionization potential of an atom which would be just 50 per cent ionized under given conditions. For the spot this level is 7.0 ± o.i volts, as compared with 8.5 ± o.i for the disk. From these quantities the percentages of ionization for disk and spot were calculated for 28 elements. By compar- ing these percentages with F0 and Y1, it was found that the amount of material per uni Publication: The Astrophysical Journal Pub Date: April 1932 DOI: 10.1086/143368 Bibcode: 1932ApJ....75..222M full text sources ADS | Related Materials (1) Part 2: 1932ApJ....75..298M