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Coronagraph observations of the coronal condensation of 4 February 1962

Zirin, H. (1970) Coronagraph observations of the coronal condensation of 4 February 1962. Solar Physics, 11 (3). pp. 497-512. ISSN 0038-0938.

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Climax coronagraph observations of the accessible Fe lines, as well as the CaXV λ5694 line at the time of the 1962 total eclipse, are analyzed. The spectra show that the ionization equilibrium of iron is not substantially changed in an intense coronal condensation, at least for the stages X through XV. The only exception is FeXV λ7059, for which density effects are important. The stability of the ionization distribution is explained by the dynamic nature of the Fe ionization, with ions entering on the high side (FeXVI and up) due to rapid heating and then cooling through the visible stages. Comparison of the ionization distributions inferred from radiative and collisional excitation of the iron lines shows that the excitation must be by collisions everywhere at the heights examined (less than 50 000 km). The iron abundance in the corona is found to be 10⁻⁴ that of hydrogen, but this figure would be reduced by the amount of cyclic excitation. The peak electron density in the condensation is 8 × 10⁹, and the peak value of the λ5694 line/ continuum ratio is 2.5, in good agreement with calculations by Chevalier and Lambert. The ratio of the infrared FeXIII lines is measured along the limb and found to vary with electron density as expected, the 10 747/10 798 ratio is 7 or less at densities much below 10⁹ and saturates at a value of 2 for densities above that amount.

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Additional Information:© 1970 Kluwer Academic Publishers. Provided by the NASA Astrophysics Data System. Received 06 October 1969; Issue Date March 1970. I am indebted to the late Bob James for obtaining the spectra, to Helen Glasco and Louise Mao for assisting with the measurements, and to David Lambert and Roger Chevalier for use of the unpublished calculations, as well as many discussions. This work was begun at the High Altitude Observatory and concluded at Caltech under sponsorship of NASA Grant NGR 05-002-034.
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NASANGR 05-002-034
Subject Keywords:Iron; Ionization Distribution; Rapid Heating; Density Effect; High Side
Issue or Number:3
Record Number:CaltechAUTHORS:20200701-065642178
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Official Citation:Zirin, H. Coronagraph observations of the coronal condensation of 4 February 1962. Sol Phys 11, 497–512 (1970).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104175
Deposited By: Tony Diaz
Deposited On:01 Jul 2020 16:38
Last Modified:01 Jul 2020 16:38

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