Hostname: page-component-78c5997874-v9fdk Total loading time: 0 Render date: 2024-11-08T05:37:33.004Z Has data issue: false hasContentIssue false
  • English
  • Français

Summary-Introduction

Published online by Cambridge University Press:  19 March 2018

J.C. Pecker  and
R. N. Thomas
J.C. Pecker
Affiliation:
Observatoire de Meudon and Boulder Laboratories-NBS
R. N. Thomas
Affiliation:
Observatoire de Meudon and Boulder Laboratories-NBS

Extract

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.

This paper is an introduction to the astronomical material underlying the Varenna Symposium on Aerodynamical Phenomena in Stellar Atmospheres. The term « aerodynamical phenomena » rather than simply « velocity fields » is used in the title of the symposium to imply that primary concern centers as much on the physical phenomena and consequences associated with the presence of velocity fields as it does simply on the velocity fields themselves. To fully appreciate this distinction between aerodynamical phenomena and velocity fields from the astronomer's viewpoint, one must consider it against the background of the classical theory (*) of stellar atmospheres, which assumes that all the properties of the atmosphere are strictly controlled by the radiation field. The thermodynamic state of the classical atmosphere is fixed by the three conditions of radiative equilibrium (no energy transport other than by radiation), hydrostatic equilibrium (no mechanical momentum transport), and local thermodynamic equilibrium at a temperature fixed by the local energy-density of the radiation field (complete coupling between radiation field and atomic degrees of freedom). Analyses of stellar spectra under the framework of this classical atmospheric model take account of the presence of velocity fields (other than thermal) only in their effect upon the atomic absorption coefficient, not in their energetic or momentum coupling to the thermodynamic state of the atmosphere. Thus, if we become interested in aerodynamic phenomena in stellar atmospheres, we must investigate the possible perturbation these velocity fields may have upon the thermodynamic state of the atmosphere. We develop a primary concern with differential motions, velocity gradients, and dissipation mechanisms — all quantities which may produce a local non-relative energy source — rather than directing our attention only at stellar rotation and uniform expansion of an atmosphere. Thus, what we call aerodynamic phenomena embraces not only velocity fields but also their influence upon the thermodynamic state of the atmosphere.

Type
Part I. Questions of General Background and Methodology Relating to Aerodynamic Phenomena in Stellar Atmospheres
Information
Symposium - International Astronomical Union , Volume 12: Aerodynamic Phenomena in Stellar Atmospheres , 1960 , pp. 1 - 43
Copyright
Copyright © Italian physical society 1960 

References

Allen, C. W. 1949, M. N. , 109, 173.Google Scholar
Athay, R. G. and Thomas, R. N. 1957, Ap. J. , 62, 3; 1958, Ap. J., 127, 96.Google Scholar
Beals, C. S. 1941, Collpq. Int. d'Ap. Actualités Sci. et Indust. , 901, 109, Paris.Google Scholar
Bell, B. 1951, Harvard Observatory , Spec. Report No. 35.Google Scholar
Bell, B. and Meltzer, A. 1959, Smith Contr. Ap. , 3, No. 5, 39.Google Scholar
Chandrasekhar, S. 1934, M. N. , 94, 16.Google Scholar
de Jager, C. 1952, Rech. Astr. Obs. Utrecht , 13, Part I, 50; 1959, Hd. d. Phys., 42, 80, Berlin.Google Scholar
Goldberg, L. 1958, Ap. J. , 127, 308.CrossRefGoogle Scholar
Goldberg, L., Mohler, O. C. and Mueller, E. A., 1959, Ap. J. , 129, 119.CrossRefGoogle Scholar
Houtgast, J. 1953, Proc. Gonv. Volta p. 33; Roma.Google Scholar
Huang, S.-S. 1952a, Ap. J. , 115, 529.CrossRefGoogle Scholar
Huang, S.-S. and Struve, O. 1960, « Stars and Star Systems, vol. 6, Astrophysics », Ed. Grenstein, and Kuiper, . (We are indebted to Dr. Huang for sending us a copy of this summary paper prior to its publication.) Google Scholar
Huang, S.-S. and Struve, O. 1952b, Ap. J. , 116, 410; 1953, Ap. J., 118, 463; 1955a, Ap. J., 121, 84; 1955b, Ap. J., 122, 103.CrossRefGoogle Scholar
Jefferies, J. T. and Thomas, R. N. 1958, Ap. J. , 667.Google Scholar
McCrea, W. H. 1929, M. N. , 89, 718.Google Scholar
Menzel, D. H. 1939, Pop. Astron. , 37, Nos. 1, 2, 3.Google Scholar
Neven, L. and de Jager, C. 1954, BAN , 12, No. 451, 103.Google Scholar
Pagel, B. E. J. 1959, Comm. l'Obs. Roy. Belg. , No. 157, 28; 1959, Vistas in Astronomy, vol. III, (London).Google Scholar
Pecker, J.-C. 1957a, C. R. , 245, 499; 1957b, C. B., 245, 639; 1959a, Ann. d'Ap., 22, 499; 1959b, Liège Colloquium on Astrophysics, 1959.Google Scholar
Pecker, J.-C., Kandel, R., Rountree, J. C. and Praderie, F., Comm. de l'Obs. Roy. Belg. 1959, Vo. 157; 351, 36, 43, 47, 53.Google Scholar
Pecker, J.C. and Vogel, E. 1960, Ann. d'Ap. , 23, 594.Google Scholar
Richardson, R. S. and Schwarschild, M. 1950, Ap. J. , 111, 351.CrossRefGoogle Scholar
Rogerson, J. B. 1957, Ap. J. , 125, 275.CrossRefGoogle Scholar
Rosseland, S. 1929, M. N. , 89, 49.Google Scholar
Sobolev, V. V. 1947, « Moving Envelopes of Stars » Russ. ed. Leningrad State Univ.; Eng. trans. by Gaposchkin, S., Harvard Un. Press, 1960.Google Scholar
Struve, O. and Elvey, C. T. 1934, Ap. J. , 79, 409.CrossRefGoogle Scholar
Suemoto, E. 1957, M. N. , 117, 2.Google Scholar
Thomas, R. N. 1948, Ap. J. , 108, 130; 1949, Ap. J., 109, 560; 1952, Ap. J., 115, 550; 1957, Ap. J., 125, 260.CrossRefGoogle Scholar
Thomas, R. N. and Athay, R. G. 1961, Physics of the Solar Chromosphere , New York, N.Y. CrossRefGoogle Scholar
Unno, W. 1959, Ap. J. , 129, 338.CrossRefGoogle Scholar
Wrubel, M. 1949, Ap. J. , 109, 67.CrossRefGoogle Scholar