Solar Physics

, Volume 54, Issue 1, pp 3–24 | Cite as

An empirical, statistical model for the formation of the cores of chromospheric Fraunhofer lines

  • Z. Suemoto
Article
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Revised:

Abstract

We describe an empirical, statistical model for the formation of the cores of chromospheric Fraunhofer lines. The model chromosphere consists of brighter structural elements with large scale motions randomly distributed in space, and above these, darker structural elements, again randomly distributed in space. Both components overlie a more uniform lower chromosphere. The probability of finding a given number of elements along a line of sight is specified by a Poisson distribution, in terms of the average number of structures along the line of sight. When this average is small, the statistical model may behave like an effectively thin plane-parallel chromosphere, even when the optical thickness of the individual structures is very large.

The model has been applied to the interpretation of Ca ii and Mg ii resonance lines, and to Hα and Hβ. By comparing computed mean intensity profiles and profiles associated with statistical intensity fluctuations with observations, a consistent set of chromospheric parameters was determined. It is tentatively concluded that the line cores are formed by structural elements whose optical thicknesses are very large at the line centre of K, located somewhere not far above 1000 km and moving with RMS velocity of about 7 km s−1.

Keywords

Statistical Model Poisson Distribution Line Centre Optical Thickness Resonance Line 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© D. Reidel Publishing Company 1977

Authors and Affiliations

  • Z. Suemoto
    • 1
  1. 1.Dept. of AstronomyUniversity of TokyoJapan

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