Observations of polar plumes with the SUMER instrument on SOHO

We present new observations of O VI 1032 Angstrom line profiles in polar plumes, and inter-plume regions, on the disk and above the limb in the north coronal hole obtained with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument on the SOHO (Solar and Heliospheric Observatory) spacecraft. On 22 May 1996, a 5 x 5 are min spectroheliogram was scanned above the north polar coronal hole with the entrance slit extending from 1.03 to 1.33 solar radii with 1.5 arc sec spatial resolution and approximate to 0.044 Angstrom per pixel spectral resolution in the wavelength range 1020-1040 Angstrom. Detailed plume structure in O VI 1032 Angstrom can be seen extending beyond 1.3 solar radii, with intensities in the plume regions 10-50% brighter, but line widths 10-15% narrower, than the inter-plume regions. Possible explanations for this observed anti-correlation between line width and intensity in the plume and inter-plume regions are discussed. We conclude that the source of the high-speed solar wind may not be polar plumes, but the inter-plume lanes associated with open magnetic field regions of the chromospheric network.