Hostname: page-component-cd9895bd7-hc48f Total loading time: 0 Render date: 2024-12-26T03:25:49.598Z Has data issue: false hasContentIssue false
  • English
  • Français

Numerical Simulation of Granular Convection: Effects on Photospheric Spectral Line Profiles

Published online by Cambridge University Press:  12 April 2016

Åke Nordlund
Åke Nordlund*
Affiliation:
Nordita, Blegdamsvej 17, Dk-2100, København Ø, Denmark

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The results of numerical simulations of the solar granulation are used to investigate the effects on photospheric apectral lines of the correlated velocity and temperature fluctuations of the convective granular motions. It is verified that the granular velocity field is the main cause for the observed broadening and strengthening of photospheric spectral lines relative to values expected from pure thermal and pressure broadening. These effects are normally referred to as being due to “macro-turbulence” and “micro-turbulence”, respectively. It is also shown that the correlated temperature and velocity fluctuations produce a “convective blue shift” in agreement with the observed blue shift of photospheric spectral lines. Reasons are given for the characteristic shapes of spectral line bisectors, and the dependence of these shapes on line strength, excitation potential, and center to limb distance are discussed.

Type
3. Conceptualizations of Turbulence
Information
International Astronomical Union Colloquium , Volume 51: Stellar Turbulence , 1980 , pp. 213 - 224
Copyright
Copyright © Springer-Verlag 1980

References

Adam, M.G., Ibbetson, P.A., Petford, A.D., 1976, Monthly Notices Roy. Ast. Soc. 177, 687 Google Scholar
Beckers, J.M., de Vegvar, P. 1978, Solar Phys. 58, 7.Google Scholar
Blackwell, D.E., Ibbetson, P.A., Petford, A.D., 1975, Monthly Notices Roy. Ast. Soc. 171, 195 Google Scholar
Blackwell, D.E., Ibbetson, P.A., Petford, A.D., Willis, R.B., 1976a, Monthly Notices Roy. Ast. Soc. 177, 219 CrossRefGoogle Scholar
Blackwell, D.E., Ibbetson, P.A., Petford, A.D., Willis, R.B., 1976b, Monthly Notices Roy. Ast. Soc. 177, 227 Google Scholar
Blackwell, D.E., Ibbetson, P.A., Petford, A.D., Shallis, M.J., 1979a, Monthly Notices Roy. Ast. Soc. 186, 633 CrossRefGoogle Scholar
Blackwell, D.E., Petford, A.D., Shallis, M.J., 1979b, Monthly Notices Roy. Ast. Soc. 186, 657 Google Scholar
Blackwell, D.E., Shallis, M.J., 1979c, Monthly Notices Roy. Ast. Soc. 186, 673 Google Scholar
Bray, R.J., Loughhead, R.E., 1967, The Solar Granulation, Chapman & Hall Ltd., London Google Scholar
Dravins, D., 1979, this colloquiumGoogle Scholar
Dravins, D., Lindegren, L., Nordlund, A., 1979, in preparationGoogle Scholar
Evans, J.C., Ramsey, L.W., Testerman, L., 1975, Astron. Astrophys. 42, 237 Google Scholar
Gustafsson, B., Olander, N., 1979, Physica Scripta, in pressGoogle Scholar
Gustafsson, B., Bell, R.A., Eriksson, K., Nordlund, A., 1975, Astron. Astrophys. 42, 407 Google Scholar
Nordlund, Å., 1976a, Astron. Astrophys. 50, 23 Google Scholar
Nordlund, Å., 1976b, in “Problems of Stellar Convection”, Lecture Notes in Physics no. 71, ed. Spiegel, E.A., Zahn, J.P. Google Scholar
Nordlund, Å., 1978, in “Astronomical Papers dedicated to Bengt Strömgren”, ed. Reiz, A., Andersen, T.; Cop. Univ. Obs.Google Scholar
Nordlund, A., 1979, this colloquiumGoogle Scholar
Stenflo, J.O., Lindegren, L., 1977, Astron. Astrophys. 59, 367 Google Scholar
Struve, O., Elvey, C.T., 1934, Astrophys. J. 79, 409 CrossRefGoogle Scholar
unsöld, A., 1955, Physik der Sterneatmospháren, Berlin, Springer Google Scholar
Wittman, A., 1979, in “Small Scale Motions on the Sun”, Mitteilungen aus dem Kiepenheuer-Institut 179 Google Scholar