Abstract
view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Study of Active Regions in the Solar Corona Observed by OSO-I. Neupert, Werner M. Abstract The extreme ultraviolet solar spectrum, including emission lines from nine successive stages of ionization of iron, was observed by OSO-I from March through June 1962. Iron line emission from specific active regions existing on the sun during that interval has been estimated for successive solar rotations by comparing data acquired when only a single active region or a group of equivalent regions, appeared on the disk, to data taken in the absence of such regions. Fluxes at radio frequencies are analyzed in the same manner and are compared to the ultraviolet observations. The relative merits of the two types of measurements in determining coronal temperatures and densities is discussed. These data, combined with Ca+ plage observations and limb observations of coronal forbidden lines, are applied to a schematic coronal model to obtain physical conditions in the coronal region associated with a Type E sunspot group at various states in its development. Using the ionization equilibrium for iron calculated by Burgess and Seaton (Monthky Notices Roy. Astron. Soc. 127, 355, 1964), we infer an electron temperature of 4.2 x 106 0K and a density increase of approximately 10 times quiet coronal values at the time maximum development of the spot group. Under these conditions Fe XVI and Fe XVII represent the predominant stages of ionization of iron. Both temperature and density decrease as activity diminishes. For the region above the residual plage, after all spots have disappeared, we obtain 3 X 106 0K and a density of two or three times quiet coronal values. Additional properties of a model of the active region, including the aI~undance of iron. are discussed. Publication: The Astronomical Journal Pub Date: April 1966 DOI: 10.1086/109889 Bibcode: 1966AJ.....71..173N full text sources ADS |
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