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/

We observed two solar active regions (NOAA regions 7563 and 7565), qui et-Sun areas, and a coronal hole region simultaneously with Goddard Sp ace Flight Center's Solar EUV Rocket Telescope and Spectrograph (SERTS ) and with the Yohkoh Soft X-ray Telescope (SXT) on 1993 August 17. SE RTS provided spatially resolved active region and quiet-Sun slit spect ra in the 280 to 420 Angstrom, wavelength range, and images in the lin es of He II lambda 303.8, Mg IX lambda 368.1, Fe XV lambda 284.1, and Fe XVI lambda lambda 335.4 and 360.8 SXT provided images through multi ple broadband filters in both the full-frame imaging mode and the part ial-frame imaging mode. The SERTS images in Fe XV (log T-max=6.33, whe re T-max is the temperature which maximizes the fractional ion abundan ce in the available ionization equilibrium calculations, i.e., the for mation temperature) and Fe XVI (log T-max=6.43) exhibit remarkable mor phological similarity to the SXT images. Whereas the Fe XV and XVI ima ges outline the loop structures seen with SXT, the cooler He II (log T -max=4.67) and Mg IX (log T-max=5.98) images outline loop footpoints. In addition, the Mg IX emission outlines other structures not necessar ily associated with the hot loops; these may be cool (T less than or s imilar to 1x10(6) K) loops. From the spatially resolved slit spectra, we obtained emission-line profiles for lines of He II lambda 303.8, Mg IX lambda 368.1, Fe XIII lambda 348.2, Fe XIV lambda 303.3, Fe XIV la mbda 334.2, Fe XVI lambda 284.1, and Fe XVI lambda 335.4 for each spat ial position. Based upon the spatial variations of the line intensitie s, active region 7563 systematically narrows when viewed with successi vely hotter lines, and appears narrowest in the broadband soft X-ray e mission. The active region width (full width at half-maximum intensity ) diminishes linearly with log T-max; the linear fit yields an extrapo lated effective log T-max of 6.51+/-0.01 for the X-ray emission. The m ost intense, central core straddles the magnetic neutral line. Active region and quiet-Sun one-dimensional temperature scans were derived fr om intensity ratios of spatially resolved SERTS slit spectral lines, a nd from coregistered SXT filter ratios. The highest plasma temperature s were measured in the most intense, central core of region 7563. The temperatures derived from Fe XVI lambda 335.4/Fe XV lambda 284.1 and F e XVI lambda 335.4/Fe XIV lambda 334.2 vary significantly (based upon the measurement uncertainties) but not greatly (factors of less than 1 .5) across the slit. The average log T values derived from the above t wo ratios for region 7563 are 6.39+/-0.04 and 6.32+/-0.02, respectivel y. Somewhat larger systematic variations were obtained from all availa ble SXT filter ratios. The average active region log T values derived from the SXT AlMgMn/thin Al, thick Al/thin Al, and thick Al/AlMgMn fil ter ratios are 6.33+/-0.03, 6.45+/-0.02, and 6.49+/-0.03, respectively . Active region and quiet-Sun one-dimensional density scans were deriv ed from intensity ratios of spatially resolved SERTS slit spectral lin es of Fe XIII and Fe XIV. The derived densities show neither systemati c nor significant variations along the slit in either the active regio n or the quiet-Sun, despite the fact that the intensities themselves v ary substantially. This indicates that the product of the volume filli ng factor and the path length (f Delta l) must be greater by factors o f 3-5 in the active region core than in the outskirts. Furthermore, th e derived active region densities are similar to 2 times the quiet-Sun densities. This density difference is adequate to explain the factor of similar to 4 intensity difference in Fe XII and Fe XIII between the active and quiet areas, but it is not adequate to explain the factor of similar to 8 intensity difference in Fe XIV between the active and quiet areas. We attribute the latter to a greater f Delta l in the act ive regions. Statistically significant Doppler shifts are not detected in region 7563 or in the quiet-Sun with any of the EUV lines.