THE DETERMINATION OF CORONAL HOLE OUTFLOW VELOCITIES BELOW 1.5 R_o USING THE 'DOPPLER DIMMING' TECHNIQUE WITH THE SUMER INSTRUMENT ON SOHO

摘要

This paper presents an attempt to evaluate the use below 1.5 R_o of the Doppler Dimming method, pioneered by the UVCS/SOHO team, who use it at larger radial distances. Following Noci et al. (1987), the theoretical model for this process has been re-evaluated, incorporating some of the more recent atomic and solar data. The model is applied to data from SUMER that was recorded above the limb in a classical polar coronal hole, during the solar minimum in May 1996. This 2-dimensional raster is capable of resolving the solar plumes. The interpretation is shown to be critically dependent on the assumed density and spatial homogeneity.