Detection and limb brightening of the H bt I n=20-19 Rydberg line in the submillimetre spectrum of the Sun
Abstract
Submillimetre spectra taken near to the solar limb with a polarizing interferometer on the James Clerk Maxwell Telescope have been compared with disk-centre spectra to reveal a limb-brightened feature whose peak intensity occurs at the predicted frequency of the n=20-19 Rydberg transition in H I at 29.622 cm-1. A shoulder on this peak, at 29.65 cm-1, has been tentatively assigned to the equivalent transition in Mg I. The H I line exhibits limb brightening of up to 9% of the disk-centre continuum intensity. The intensity of the Mg I line is about half of the H I line intensity across the observed region near to the limb. Widths of the H I line are between 0.020 and 0.027 cm-1, smaller than predicted by current models of this line in the Sun's spectrum. These measurements represent the highest-n Rydberg lines detected to date in the solar spectrum. The measured line intensity, line width, limb brightening and the relative heights of the contributions from H I and Mg I place constraints upon further modelling of the solar atmosphere.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- May 2000
- Bibcode:
- 2000A&A...357..757C
- Keywords:
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- LINE: IDENTIFICATION;
- SUN: GENERAL;
- SUN: ATMOSPHERE;
- SUN: INFRARED