A DOPPLER DIMMING DETERMINATION OF CORONAL OUTFLOW VELOCITY

Outflow velocities in a polar coronal hole are derived from observatio ns made during a 1982 sounding rocket flight. The velocity results are derived from a Doppler dimming analysis of resonantly scattered H I L yalpha. This analysis indicates radial outflow velocities of 217 km s- 1 at 2 R. from Sun-center with an uncertainty range of 153 to 251 km s -1 at a confidence level of 67%. These results are best characterized as strong evidence for supersonic outflow within 2 R. of Sun-center in a polar coronal hole. Several means for obtaining improved accuracy i n future observations are discussed.