Spectrophotometric Observations of the Light of the Night Sky.

Abstract

view Abstract Citations (22) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectrophotometric Observations of the Light of the Night Sky. Elvey, C. T. ; Farnsworth, Alice H. Abstract Spectrophotometric observations of the light of the night sky have been made for the stronger lines of the visual region of the spectrum to determine (1) the variation of intensity with zenith distance to obtain a measure of the height of the auroral layer and (2) the curves of nocturnal variation of intensity. The variation of intensity with zenith distance indicates a height of 500 km for the auroral layer pro- ducing the red and green auroral lines, as well as the line of uncertain origin at A 6560. This is greater than the height obtained for the infrared radiations, 125 km. Curves of nocturnal variations of intensity were obtained at Bosque Alegre, Argentina; at Potrerillos, Chile; in the southern New England states; and at the McDonald Observatory. There were no marked differences with geographical position; however, the observations were not simultaneous, and the terres- trial magnetic activity was generally low at the times the observations were made. The sodium line is relatively constant through the night, but the enhancement at both evening and morning twilights-a resonance effect from the sun illuminating sodium atoms in the upper atmosphere-indicates that the distribution of sodium between levels of 70 and 115 km is exponential with height and in agreement with that of the total number of molecules. The green auroral line is found to be relatively constant through- out the night and through both twilights. The reported maximum near midnight has not been confirmed. The red auroral line, also a radiation of the oxygen atom, has remarkable twilight effects, the one in the evening lasting for three or four hours after the end of twilight and the morning effect beginning two hours before dawn. The morning twilight effect is probably due to the illumination by the sun of the atoms in the upper atmosphere; but the evening effect is composite, there being, in addition, an excess intensity which decreases exponentially with time and which comes from the atoms that are already in the shadow of the earth. That portion of the twilight effect which is related to the direct illumination of the sun indi- cates a much larger proportion of oxygen atoms in the upper atmosphere than theoretical considerations require Publication: The Astrophysical Journal Pub Date: November 1942 DOI: 10.1086/144477 Bibcode: 1942ApJ....96..451E full text sources ADS |