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Diffusion of helium in the Sun

Abstract

I have reduced the set of diffusion and flow equations developed by Burgers for a multi-component gas to a workable scheme for the actual evaluation of the relative diffusion of hydrogen and helium in stars. Previous analyses have used the Aller and Chapman equations, which apply only to trace constitutents and whose coefficients are not believed to be as accurate as Burgers'. Furthermore, the resulting equations have been combined consistently with Paczynski's stellar evolution code to demonstrate small but significant effects in the Sun, from the thermal and gravitational settling of Helium. The core helium content of a 1 M star goes up about 0.04 and the surface helium content down by about -0.03 in 4.5 10/sup 9/ years. The results are still somewhat uncertain because of uncertainties in the underlying plasma physics, and further research is suggested. In any case, the diffusion process speeds up with time, due to increased temperature gradient, and it will be of interest to follow the process in older stars and in later stellar evolution.
Authors:
Noerdlinger, P D; [1]  Amsterdam Univ. (Netherlands). Sterrenkundig Instituut)
  1. Michigan State Univ., East Lansing (USA). Dept. of Astronomy and Astrophysics
Publication Date:
May 01, 1977
Product Type:
Journal Article
Reference Number:
AIX-09-353319; EDB-78-065911
Resource Relation:
Journal Name: Astron. Astrophys.; (Germany, Federal Republic of); Journal Volume: 57:3
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; STARS; PERMEABILITY; SUN; DIFFUSION; HELIUM; STAR EVOLUTION; TIME DEPENDENCE; CRYOGENIC FLUIDS; ELEMENTS; FLUIDS; NONMETALS; RARE GASES; 640104* - Astrophysics & Cosmology- Solar Phenomena; 640102 - Astrophysics & Cosmology- Stars & Quasi-Stellar, Radio & X-Ray Sources
OSTI ID:
5060595
Country of Origin:
Germany
Language:
English
Other Identifying Numbers:
Journal ID: CODEN: AAEJA
Submitting Site:
INIS
Size:
Pages: 407-415
Announcement Date:
Feb 01, 1978

Citation Formats

Noerdlinger, P D, and Amsterdam Univ. (Netherlands). Sterrenkundig Instituut). Diffusion of helium in the Sun. Germany: N. p., 1977. Web.
Noerdlinger, P D, & Amsterdam Univ. (Netherlands). Sterrenkundig Instituut). Diffusion of helium in the Sun. Germany.
Noerdlinger, P D, and Amsterdam Univ. (Netherlands). Sterrenkundig Instituut). 1977. "Diffusion of helium in the Sun." Germany.
@misc{etde_5060595,
title = {Diffusion of helium in the Sun}
author = {Noerdlinger, P D, and Amsterdam Univ. (Netherlands). Sterrenkundig Instituut)}
abstractNote = {I have reduced the set of diffusion and flow equations developed by Burgers for a multi-component gas to a workable scheme for the actual evaluation of the relative diffusion of hydrogen and helium in stars. Previous analyses have used the Aller and Chapman equations, which apply only to trace constitutents and whose coefficients are not believed to be as accurate as Burgers'. Furthermore, the resulting equations have been combined consistently with Paczynski's stellar evolution code to demonstrate small but significant effects in the Sun, from the thermal and gravitational settling of Helium. The core helium content of a 1 M star goes up about 0.04 and the surface helium content down by about -0.03 in 4.5 10/sup 9/ years. The results are still somewhat uncertain because of uncertainties in the underlying plasma physics, and further research is suggested. In any case, the diffusion process speeds up with time, due to increased temperature gradient, and it will be of interest to follow the process in older stars and in later stellar evolution.}
journal = []
volume = {57:3}
journal type = {AC}
place = {Germany}
year = {1977}
month = {May}
}