Abstract
Three quiescent prominences were observed in the Ca ii K-line and a fourth one also in the H-line at Oslo Solar Observatory, Harestua, and reduced by Rustad (1974) and by Engvold et al. (1980). These data are used to study the distribution of the line-of-sight velocity component, N(u 0). It is pointed out that in a stationary and isotropic case, N(u 0) should be a gaussian distribution. For each of the sets of measurements gaussians were therefore fitted by a least square procedure. The range in observed velocities varies considerably between the prominences. For the best observed prominence more than 70% of the kinetic energy is in the supersonic range. In the other cases none or only an insignificant part of the observations exceed the velocity of sound. Considerable deviations from gaussian distributions are apparent for the smallest velocities. This distortion shows up conspicuously in the slope of the energy spectrum, a parameter that may be used as a rough measure of spectral resolution.
If it is assumed that we have to do with MHD-turbulence as described by Kraichnan (1965), a characteristic relationship should exist between velocity and eddy size. When supersonic velocities are present, compressibility effects may severely alter this relationship. The possibility of observational confirmation is discussed.
If a turbulent velocity field is indeed present, the heat conductivity and other transport coefficients may be significantly altered as compared to the atomic values.
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References
Brahde, R. and Engvold, O.: 1981, private communication.
Dunn, R. B.: 1978, Osservazioni e Memorie dell Osservatorio Astrofisico di Arcetri 106, 135.
Engvold, O.: 1972, Solar Phys. 23, 346.
Engvold, O.: 1976, Solar Phys. 49, 283.
Engvold, O. and McKim Malville, J.: 1977, Solar Phys. 52, 369.
Engvold, O., Wiehr, E., and Wittmann, A.: 1980, Astron. Astrophys. 85, 326.
Hirayama, T.: 1978, in E. Jensen, P. Maltby, and F. Q. Orrall (eds.), ‘Physics of Solar Prominences’, IAU Colloq. 44, 4.
Hirschfelder, J. O., Curtiss, C. F., and Bird, R. B.: 1964, Molecular Theory of Gases and Liquids, John Wiley & Sons, New York, London.
Kraichnan, R. H.: 1965, Phys. Fluids 8, 1385.
Lang, K. R.: 1974, Astrophysical Formulae, Springer-Verlag, Berlin, Heidelberg, New York.
Leroy, J. L.: 1978, in E. Jensen, P. Maltby, and F. Q. Orrall (eds.), ‘Physics of Solar Prominences’, IAU Colloq. 44, 56.
Maxwell, J. C.: 1890, The Scientific Papers of J. C. Maxwell, Cambridge at the University Press, Vol. I, p. 377.
Rust, D. M.: 1972, Air Force Survey in Geophysics, No. 237.
Rustad, B. M.: 1974, Thesis, Institute of Theoretical Astrophysics, Univ. of Oslo.
Shkarofsky, I. P., Johnston, T. W, and Bachynski, M. P.: 1966, The Particle Kinetics of Plasmas, Addison-Wesley Publishing Company, Reading, Mass.
Tandberg-Hanssen, E.: 1974, Solar Prominences, D. Reidel Publ. Co., Dordrecht, Holland.
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Jensen, E. Velocity fields in quiescent prominences. Sol Phys 77, 109–119 (1982). https://doi.org/10.1007/BF00156099
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DOI: https://doi.org/10.1007/BF00156099