New measurements of the solar limb emission in the OI 777.4 and 844.6 nanometer lines

Authors
Citation
Mj. Penn, New measurements of the solar limb emission in the OI 777.4 and 844.6 nanometer lines, ASTROPHYS J, 518(2), 1999, pp. L131-L134
Citations number
20
Categorie Soggetti
Space Sciences
Journal title
ASTROPHYSICAL JOURNAL
ISSN journal
0004637X → ACNP
Volume
518
Issue
2
Year of publication
1999
Part
2
Pages
L131 - L134
Database
ISI
SICI code
0004-637X(19990620)518:2<L131:NMOTSL>2.0.ZU;2-Y
Abstract
Slit spectra of the solar limb emission in the 777.4 and 844.6 nm O I lines are calibrated against the solar disk center brightness. Data from CCD spe ctrograph instruments at two different observatories show limb emission wit h identical line intensities and measure a value of R-4 = Sigma I(844.6 nm) / Sigma I(777.4 nm) = 0.20 +/- 0.02, very different from the ratios compute d from early photographic measurements of these Lines. Implied by this new value of R-4 is that O I lines in the solar chromosphere are formed in regi ons with electron densities log (N-e) > 11.5 and that collisional excitatio n is more important than the photoexcitation by accidental resonance mechan ism.