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Inhomogeneous structure of the solar chromosphere from Lyman-continuum data

✍ Scribed by J. E. Vernazza; R. W. Noyes

Publisher
Springer
Year
1972
Tongue
English
Weight
874 KB
Volume
22
Category
Article
ISSN
0038-0938

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✦ Synopsis

We describe a new model of the chromosphere based on Lyman-continuum observations by Harvard spectrometers aboard the satellites OSO 4 and OSO 6. The model assumes (a) that a random distribution of optically thick inhomogeneities overlies a plane-parallel homogeneous atmosphere, and (b) that the Lyman continuum in the chromosphere is optically thick and the only significant opacity source between 600 and 912/~.

The temperature, gas pressure, electron pressure, particle densities, and bl (the hydrogen groundstate departure coefficient) are calculated as a function of height in the chromosphere.

The model reproduces the observed quiet-region intensities in the Lyman continuum. The inhomogeneous structures, which we believe to be spicules, are inferred to be optically thick in the Lyman continuum and to have a source function below that of the mean chromosphere. If they are also optically thick in the free-free (millimeter) continuum and cooler than about 5000K, they could produce the observed limb darkening at 1 and 3 ram. Such low temperatures are at odds with current spicule models, but could exist in the cores of spicules.

The Lyman-continuum emission shortward of 750/~ shows an excess emission over that predicted by the above model. This is found to be consistent with the existence of a temperature plateau with T ~ 22000K in the very high chromosphere.

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