Quiet Sun chromospheric network observed from SKYLAB
Spectra between 1200 and 1560 A of a supergranulation cell interior and cell boundary observed near Sun center are discussed. Absolute intensities are given for selected lines of chromospheric and transition-zone ions. The spectra were obtained by the NRL normal-incidence spectrograph on Skylab. The spectral resolution is 0.06 A, and the spatial resolution is 2'' x 60''. The width of the cell boundary was found to be approx.10'' in lines of low-temperature ions such as C II and O I, and approx.6'' in lines of high-temperature ions such as C IV and N V. The brightness contrast between cell interior and boundary is an increasing functions of the characteristic emitting temperature of the observed lines between approx.8 x 10/sup 3/ K and approx.1.3 x 10/sup 5/ K. The maximum contrast is observed in O IV and is about a factor of 5. Above and below the temperature of O cV the contrast falls, and is about 1.5 for lines of O I and S I. The full widths at half-maximum (FWHM) of the optically thin lines are the same over cell interiors and cell boundaries, and agree with the widths observed in limb spectra. From the FWHM of the 1207 A Si III line, optical depths at line center of 5.8 and 1.6 are deduced for the cell boundary and cell interior, respectively. The electron density in the cell boundary appears to be nearly equal to the cell interior density. From the intensities of the intersystem lines of O IV (2s/sup 2/2p /sup 2/P/sub J//sup 0/-2s2p/sup 2/ /sup 4/P/sub J//sub prime/) measured above the limb in the quiet Sun, an electron density of 4.6 x 10/sup 9/ cm/sup -3/ is derived for the O IV emitting region. This density does not change within the first 8000 km above the limb, and is about a factor of 1.6 lower in the north polar coronal hole. Assuming a constant pressure, the characteristic height of the Si III emitting region is approx.840 km in the boundary and approx.380 km in the cell interior. The results are compared with a recent model by Gabriel. (AIP)
- OSTI ID:
- 7344747
- Journal Information:
- Astrophys. J.; (United States), Vol. 209:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
CHROMOSPHERE
ULTRAVIOLET SPECTRA
CHEMICAL COMPOSITION
ELECTRON DENSITY
LINE WIDTHS
OPACITY
SOLAR CORONA
SOLAR GRANULATION
ATMOSPHERES
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SPECTRA
640104* - Astrophysics & Cosmology- Solar Phenomena