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The Galileo and Pioneer Venus ultraviolet spectrometer experiments - Solar Lyman-alpha latitude variation at solar maximum from interplanetary Lyman-alpha observations
Pryor, W. R.; Ajello, J. M.; Barth, C. A.; Hord, C. W.; Stewart, A. I. F.; Simmons, K. E.; McClintock, W. E.; Sandel, B. R.; Shemansky, D. E.
AA(Colorado, University, Boulder), AB(Colorado, University, Boulder; JPL, Pasadena, CA), AC(Colorado, University, Boulder), AD(Colorado, University, Boulder), AE(Colorado, University, Boulder), AF(Colorado, University, Boulder), AG(Colorado, University, Boulder), AH(Colorado, University, Boulder), AI(Colorado, University, Boulder)
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 394, no. 1, July 20, 1992, p. 363-377. Research supported by NASA. (ApJ Homepage)
Publication Date:
Solar Physics
NASA/STI Keywords:
Galileo Spacecraft, Lyman Alpha Radiation, Pioneer Venus Spacecraft, Solar Activity, Solar Radiation, Ultraviolet Spectrometers, Brightness Distribution, Hydrogen Atoms, Interplanetary Medium, Solar Cycles, Solar Wind, Stellar Models
Bibliographic Code:


Solar Ly-alpha latitude variation at solar maximum is examined on the basis of interplanetary Ly-alpha observations made during the Galileo and Pioneer Venus UV spectrometer experiments. A comparison is made of the latitude variation of the interplanetary (IP) Ly-alpha signal in 1986 at solar minimum from Pioneer Venus and in 1990 at solar maximum from Galileo. The Galileo EUV spectrometer shows that a large enhancement of the IP Ly-alpha emission occurred over the intervening four years near the solar equator. An IP Ly-alpha model is developed which considers the latitude variation of the solar Ly-alpha flux. The model fit to the data shows a 25-percent decrease of the full disk solar Ly-alpha flux from solar equator to solar pole in 1990. A detailed study of the Galileo IP Ly-alpha observations on day-of-year 190, 193, 197, and 200 in 1990 reveals that large variations occur in response to the 27-d solar variation. Analysis of these data shows that a maximum variation of 20 percent can be expected in the IP Ly-alpha upwind intensity over this 27-d period.

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Database: Astronomy
arXiv e-prints