SOHO Joint Operations Programme 90 ================================== CDS/TRACE - 18th May 1998 ------------------------- Polar Plumes ------------- P.R. Young, J. Klimchuk & C.C. Kankelborg The combined strengths of the spectroscopic power of CDS and the high spatial and temporal resolution of TRACE will provide excellent opportunities for the analysis of plume properties. Analysis of CDS observations (Young, 1998, Young and Klimchuk, 1998) show that above their base, plumes have a near uniform temperature of between logT=6.0 and 6.1, whereas the base can reach values of around 6.3. NIS has excellent coverage of these temperature regions, from Si VIII (logT=5.8), through Mg VIII (logT=5.9), Mg IX (logT=6.0), Mg X (logT=6.1) and Si XII (logT=6.3), while there are density diagnostics from Mg VIII (logT=5.9), Si IX (logT=6.0), Si X (logT=6.1) and Fe XIV (logT=6.3). Recent EIT observations (DeForest et al. 1998) show that the plumes appear in the Fe IX/X and Fe XII filters. Temporally, the plumes are found to be relatively stable on large spatial scales (> 30 arcsec), but on smaller scales considerable variation is found with "filamentary structures brightening and fading apparently randomly" (DeForest et al. 1998). The improved spatial resolution of TRACE will allow the evolution of these small-scale structures to be followed in more detail. If possible, CDS could use real time pointing for these observations. CDS 1) Repeats of (FFNARR30, 60x195arcsec, 58 mins) OR FOR REAL TIME POINTING 1) Context raster (RT_MON, 4'x4', 42 mins) 2) Repeat rasters (RT_PLUMES, 1'x3', 23 mins) Duration: 4-6 hours TRACE Contact: Charles Kankelborg Suggested sequence(s): cck.northpolar.fan.multi - takes 3 successive pointings above limb. First pointing is on-limb and takes all wavelengths. The second and third are above the limb and take Fe IX/X and Fe XII. The total duration of one run depends on the exposure times used but is likely to be 3-15 mins.