Structure of the solar chromosphere. III. Models of the EUV brightness components of the quiet sun

Journal Article · Wed Apr 01 04:00:00 EST 1981 · Astrophys. J., Suppl. Ser.; (United States)

DOI:https://doi.org/10.1086/190731· OSTI ID:5990777

Vernazza, J E; Avrett, E H; Loeser, R

Skylab observations of the quiet Sun in the EUV wavelength range 40--140 nm show the inhomogeneous structure of the chromosphere. We use these observations to determine separate chromospheric models for six observed brightness components, ranging from a dark cell center to a very bright network element. In each case we solve the non--LTE radiative transfer, statistical equilibrium, and hydrostatic equilibrium equations to determine the temperature-density stratification that produces a calculated spectrum in best agreement with the observed one. Our hydrogen calculations are carried out with an atomic model consisting of eight explicit levels and supplementary levels 9--12. We account for the effects of partial frequency redistribution in the formation of the hydrogen L..cap alpha.. and L..beta.. lines and the resonance lines of Ca II and Mg II. To obtain the results shown here we carry out non--LTE calculations for H, H/sup -/, C, Si, Fe, Mg, Al, He, He II, Ca II, Mg II, and several other atoms and ions. We obtain good agreement between observed and calculated intensities in the L..cap alpha.. and L..beta.. lines, the Lyman continuum, and other continua in the 40--140 nm range. We base our temperature minimum determination on continuum observations in the 135--168 nm range but obtain minimum temperature values which are lower than implied by the Ca II and Mg II lines and recent microwave observations. In the upper chromosphere our models are in good agreement with those obtained by Basri et al. from a study of the observed L..cap alpha.. line. However, the temperature reduction in the low chromosphere proposed by Basri et al. is a consequence of their assumption of LTE for the carbon continuum which causes a spurious enhancement of the computed intensity in the L..cap alpha.. wings. Finally, we compute the net radiative cooling rates for the atoms and ions listed above.

• Research Organization: Harvard-Smithsonian Center for Astrophysics
• OSTI ID: 5990777
• Journal Information: Astrophys. J., Suppl. Ser.; (United States), Journal Name: Astrophys. J., Suppl. Ser.; (United States) Vol. 45:4; ISSN APJSA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
CHROMOSPHERE
COOLING
ELECTROMAGNETIC RADIATION
ENERGY TRANSFER
EXTREME ULTRAVIOLET RADIATION
HEAT TRANSFER
RADIANT HEAT TRANSFER
RADIATIONS
RADIATIVE COOLING
SOLAR ATMOSPHERE
ULTRAVIOLET RADIATION