SUMER study #2216: Quiescent prominence

Study Description

• date, time: 30.Jun.00 - 12.Jul.00
• field of view: various positions near limb
• slit: 1.0 arcsec x 120 arcsec (number 4)
• raster step size: 0.0 arcsec (0 elementary steps)
• exposure time: 120 seconds
• telemetry: 97 images of 1024 spectral x 120 spatial pixels (format 4)
• compression: quasilog-min-max (method 5)
• wavelengths:
  932.00 Å on reference pixel 510 of Detector A (13 images)
  1080.00 Å on reference pixel 512 of Detector A (24 images)
  1247.00 Å on reference pixel 513 of Detector A (12 images)
  1267.00 Å on reference pixel 512 of Detector A (12 images)
  1318.50 Å on reference pixel 510 of Detector A (24 images)
  1560.00 Å on reference pixel 511 of Detector A (12 images)
• rotation compensation: no
• binning: no spectral, no spatial
• on-board flat field correction: no

Remarks: The study was initiated by E. Wiehr (Univ. Göttingen) and was part of SOHO Campaign #6480. - The study was run 15 times, of which 2 were interrupted and 13 were complete (approx. 4 hours duration). Each time, the SUMER slit pointed to a certain position off-limb to let a prominence cross. Images were taken with periodically changing spectral windows.

Notes on Individual Studies

04.Jul.00:The lower part of the slit is on the disk. The middle part covers a prominence directly above the limb. At the northern edge of the prominence strong velocities can be observed, first shifted to the red, then to the blue. The prominence is hardly visible in the N I line.
05.Jul.00: The slit position was changed by some arcsec to follow the prominence. A structured, moving object is visible above the limb, covering approx. half of the slit. Small subsets at its northern edge are strongly redshifted, with an average of 67 km/s.
06.Jul.00: A small structure is visible, directly above the limb. It is redshifted with approx. 40 km/s.
07.Jul.00: The slit was changed to another position on the NE limb. The whole slit covers unstructured plasma above the limb, with homogeneous line widths and little dynamic.
08.Jul.00: As before; slightly more structure when darker regions pass the slit.
09.Jul.00: As before. - Later that day, the prominence must have disappeared.
10.Jul.00: For the most part of the first run, no structure is visible, just stray light. At the end, small loop structures appear high above the limb, which are strongly redshifted.
During the second run (three hours later) these loop structures cross the slit, most of them strongly redshifted (approx. 90 km/s). They are only visible in temperatures between 14 000 K (Si II) and 140 000 K (S IV) in the 1385 Å spectral window, not in neutral lines or coronal lines.
12.Jul.00: The slit images show the first run (24 stripes) together with the second run (incomplete, 13 stripes), that was started two hours later. - The position was changed to the SE limb. Approx. one third of the slit below the limb covers unstructured plasma, which is blueshifted at its lower border.

IED, 23.Nov.01