Forbidden Spectral Lines from the Solar Corona Below 1000 \AA

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Session 44 -- Solar Observations and Theory
Display presentation, Tuesday, 10, 1995, 9:20am - 6:30pm

[44.13] Forbidden Spectral Lines from the Solar Corona Below 1000 \AA

William E. Behring (NASA Goddard Space Flight Center)

Visible wavelength spectral lines formed in the solar corona created great interest when their origin in the forbidden transitions of highly ionized atoms was first discovered by W. Grotrian and B. Edlen, because that origin implied a temperature of about one million degrees K for the corona. These lines have since been discussed by many investigators. Additional forbidden lines in the 1000 to 2000 \AA\ spectral region have since been discussed by Feldman and Doschek, and other authors. However, not as much attention has been paid to the forbidden coronal lines in the wavelength region below 1000 \AA, a regime in which also appear many strong lines which are permitted by the electric dipole selection rules. Many of these lines, both predicted and observed, have been reviewed by Kaufman and Sugar (1986). Besides their intrinsic interest, they may serve in combination with the permitted lines as density diagnostics when the coronal density is not too high. They may even serve this purpose in the low density parts of solar flares, if such regions exist.

This paper will discuss in particular some of those lines which may be expected in the Mg I and Be I sequences, as well as offer a brief discussion of other isoelectronic sequences which may produce observable forbidden lines at wavelengths below 1000 \AA.

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