Active region 7563 and quiet-sun one-dimensional density scans were derived from intensity ratios of spatially resolved SERTS-93 slit spectral lines of Fe XIII and Fe XIV.  Figure 1(a) shows the active region density scan derived from the Fe XIV ratio 353.9/334.2, and 1(b) shows the density scan derived from the Fe XIII ratio 359.7/348.2.  Here ``density'' is understood to mean the density of the emitting plasma, which may fill only a fraction, f, of the total volume along the line of sight.  The derived densities show neither systematic nor significant variations along the slit in either the active region or the quiet-sun, despite the fact that the intensities themselves vary substantially.  This indicates that the product of the volume filling factor and the path length (fL) must be greater by factors of 3 - 5 in the active region core than in the outskirts.  Furthermore, the derived active region densities are about 2 times the quiet-sun densities. This density difference is adequate to explain the factor about 4 times the intensity difference in Fe XII and Fe XIII between the active and quiet areas, but it is not adequate to explain the factor 8 intensity difference in Fe XIV between the active and quiet areas. We attribute the latter to a greater fL in the active region.

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"The Structure and Properties of Solar Active Regions and Quiet-Sun Areas Observed in Soft X-Rays with Yohkoh/SXT, and in the Extreme Ultraviolet with SERTS," J. W. Brosius, J. M. Davila, R. J. Thomas,   J. L. R. Saba, H. Hara, and B. C. Monsignori-Fossi, Ap. J. 477, 969  (1997).

 

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Last Revised: Wednesday, 29-Nov-2006 07:36:52 EST

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