A comparison showing simultaneous Yohkoh image with SERTS Mg IX 368 contours overlaid

Comparison of Yohkoh image with SERTS Fe XV 284 contours overlaid showing coronal loop structure

Comparison of simultaneous Kitt Peak magnetogram and the SERTS He II 304 contours showing that He II emission is concentrated near loop footpoints

Simultaneous Yohkoh observations were obtained for the 1993 and 1995 flights. The coordinated data show that SERTS images in the hot, coronal Fe XV (2.0 MK; above, middle) and Fe XVI (2.5 MK) ions show nearly identical loop structures as those seen in the simultaneous Yohkoh SXT images. Further, SERTS images in the cooler Mg IX (1.0 MK; above, left) and He II ions delineate loop footpoints and possibly cool loops. In addition, the temperatures derived from line ratios using SERTS data agree with temperatures derived from filter ratios using Yohkoh data.

The figure on the above right shows that the He II emission is located at regions of opposite polarity in the photosphere, further indicating that these are indeed the footprints of coronal loops. This basic morphology indicates that photoionization plays an unimportant role in the excitation of He 304 in the transition 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

Responsible NASA Official: joseph.davila@gsfc.nasa.gov
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