2014ApJ...784L..39K


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.20CEST20:10:51

2014ApJ...784L..39K - Astrophys. J., 784, L39 (2014/April-1)

Intensity enhancement of O VI ultraviolet emission lines in solar spectra due to opacity.

KEENAN F.P., DOYLE J.G., MADJARSKA M.S., ROSE S.J., BOWLER L.A., BRITTON J., McCRINK L. and MATHIOUDAKIS M.

Abstract (from CDS):

Opacity is a property of many plasmas. It is normally expected that if an emission line in a plasma becomes optically thick, then its intensity ratio to that of another transition that remains optically thin should decrease. However, radiative transfer calculations undertaken both by ourselves and others predict that under certain conditions the intensity ratio of an optically thick to an optically thin line can show an increase over the optically thin value, indicating an enhancement in the former. These conditions include the geometry of the emitting plasma and its orientation to the observer. A similar effect can take place between lines of differing optical depths. While previous observational studies have focused on stellar point sources, here we investigate the spatially resolved solar atmosphere using measurements of the I(1032 Å)/I(1038 Å) intensity ratio of O VI in several regions obtained with the Solar Ultraviolet Measurements of Emitted Radiation instrument on board the Solar and Heliospheric Observatory satellite. We find several I(1032 Å)/I(1038 Å) ratios observed on the disk to be significantly larger than the optically thin value of 2.0, providing the first detection (to our knowledge) of intensity enhancement in the ratio arising from opacity effects in the solar atmosphere. The agreement between observation and theory is excellent and confirms that the O VI emission originates from a slab-like geometry in the solar atmosphere, rather than from cylindrical structures.

Abstract Copyright:

Journal keyword(s): opacity - radiative transfer - Sun: transition region - Sun: UV radiation

Simbad objects: 4

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Number of rows : 4

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 * eps Eri BY* 03 32 55.8449634 -09 27 29.731165 5.19 4.61 3.73 3.00 2.54 K2V 1658 1
2 V* V645 Cen Fl* 14 29 42.9451234609 -62 40 46.170818907 14.21 12.95 11.13 9.45 7.41 M5.5Ve 885 0
3 V* EV Lac Fl* 22 46 49.7311740821 +44 20 02.372223230   11.85 10.26 9.89   M4.0V 777 2
4 HD 224085 RS* 23 55 04.0516465022 +28 38 01.248194500 8.88 8.20   6.9   K2+IVeFe-1 675 0

    Equat.    Gal    SGal    Ecl

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2019.10.20-20:10:51

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