as possible of the southern polar area. In addition, to improve the signal to noise ratio of the EUVI images, a longer exposure time and a smaller compression were applied. The image pairs chosen in this work have 20 s exposure time, compared to the normal exposure time of 2 s. The images were compressed by the format ICER (a wavelet-based image compression file format) 4 which requires two times the storage of images obtained after applying the usual ICER 6 compression used ordinarily for EUVI images at 17.1 nm. In Figure \[fig:euvi\_0407\], the southern polar cap in both EUVI views is presented with five plume pairs marked by numbers below them.

In parallel, SUMER performed a raster scan from 2007-04-07 01:01 UTC to 2007-04-08 12:19 UTC in the southern corona. The scan direction was from solar west to east. The details of the SUMER observations can be found in @Curdt:etal:2008. To combine with 3D plume geometry, we derived the electron density map from the emission line pair Si[viii]{} at 144.0 nm and 144.6 nm, the electron temperature map from line pair Mg[ix]{} at 70.6 nm and 75.0 nm, and the LOS Doppler shift map from the O[vi]{} at 103.2 