Preliminary intensities of Balmer lines from the flash spectrum of the 1952 solar eclipse.

Abstract

view Abstract Citations (4) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Preliminary intensities of Balmer lines from the flash spectrum of the 1952 solar eclipse. Athay, R. G. ; Billings, D. E. ; Evans, J. W. ; Roberts, W. O. Abstract Spectrographic observations of the flash spectrum at the February 25, 1952 solar eclipse at Khartoum, Sudan, were made by the High Altitude Observatory of Harvard University and University of Colorado. A primary purpose of the expedition was to obtain information about the hydrogen Balmer and Paschen series. This information, in turn, will be used to determine the electron temperature and electron density as a function of height in the chromosphere. The observations employed three slitless spectrographs covering the spectral range X88oo to X340o. *Of papers presented at the Eighty-eighth Meeting of the American Astronomical Society, Amherst, Mass., Dec. 28-31, 1952. We obtained 29 pairs of visible and 17 pairs of ultraviolet spectrograms from X6400 to X3400, which are of satisfactory quality. The 16 infrared spectrograms X88oo to X6100 are underexposed. Imaged on the film during each exposure were two simultaneous spectra, the pair having an intensity ratio approximately 30:1. Each exposure also contained a data panel. The data panel included clocks for determining the beginning and end of each exposure and a photographic step-wedge for checking the characteristic curve. Standard exposures from a tungsten ribbon-filament lamp taken on the same roll of film as the eclipse spectrograms, but separately processed, provide data for a first approximation to the characteristic curve at any desired wave length. Corrections carried out by comparing densities in the corresponding light and dark spectral images will then give us reliable characteristic curves. The distribution of densities in the coronal continuum gives further information for improving the accuracy of the characteristic curve. More direct determination of the characteristic curves is not possible because a part of the standardizing program failed at the time of the eclipse. Using the approximate characteristic curve obtained from the standard exposures, we made preliminary measures of the intensities of the Balmer lines near the series limit on 12 spectrograms at second contact. For this we worked from positive prints of the original spectra. The heights at which measurements were made extend from 700 km to 1930 km above the base of the chromosphere, with observations every 108 km. We found that the intensity of H31 is measurable to a height of 2150 km and the intensity of H23 is measurable to 2700 km. In some spectrograms a tentative identification shows H34, H35, and H36 to be resolved. We are now initiating a more complete and more accurate reduction of the data, working from the original films. The eclipse program of the High Altitude Observatory is supported by the Naval Research Laboratory, Office of Naval Research, and has been conducted in close collaboration with the Laboratory. Three of the four authors are connected with the High Altitude Observatory, J. W. Evans with the Upper Air Research Observatory. High A ititude Observatory, Boulder, Cob., and Upper Air Research Observatory, Sacramento Peak, Clouderoft, N. Mex. Publication: The Astronomical Journal Pub Date: 1953 DOI: 10.1086/106908 Bibcode: 1953AJ.....58R..33A full text sources ADS |