Anomalous ionization in the umbrae of sunspots

Journal Article · Mon Jan 01 04:00:00 EST 1973 · Mon. Notic. Roy. Astron. Soc., v. 165, no. 1, pp. 61-76

DOI:https://doi.org/10.1093/mnras/165.1.61· OSTI ID:4361376

Blackwell, D E; Mallia, E A

New observations are presented of sunspot spectra in regions containing lines of ionlzed elements, obtained with the rapid scanning spectrometer at the Oxford--Gornergrat Observatory. The umbral spectra are corrected for scattered light from penumbra and photosphere by making use of scans of the solar limb and sky background. The corrected spectra show anomalously strong lines of Fe II and Cr H. Observation of the anomaly for Fe II depends critically on the accuracy of the scattered light measurement. A numerical experiment showed that the measured value of 26% for the relevant spot is unlikely to be greatly in error. These anomalies cannot be explained in terms of a nonhomogeneous model of an umbra in which there is a state of L.T.E. in each component, and it seems probable that the lines arise from a nonequilibrium mechanism. The possible presence of a similar anomaly in the spectra of magnetic stars is briefly discussed. (auth)

• Research Organization: Oxford Univ.
• NSA Number: NSA-29-019204
• OSTI ID: 4361376
• Journal Information: Mon. Notic. Roy. Astron. Soc., v. 165, no. 1, pp. 61-76, Journal Name: Mon. Notic. Roy. Astron. Soc., v. 165, no. 1, pp. 61-76; ISSN MNRAA
• Country of Publication: United Kingdom
• Language: English

Related Subjects

*SUNSPOTS-- SPECTRA
ATOMS
N56400* --Physics (Astrophysics & Cosmology)--Solar Phenomena
PHOTOSPHERE
SCATTERING
VISIBLE RADIATION