Measurements of coronal kinetic temperatures from 1.5 to 3 solar radii

A rocket-borne Lα coronagraph has been used to make the first measurements of the spectral line profile of resonantly scattered hydrogen Lα coronal radiation between 1.5 and 3 solar radii. These data provide, for the first time, direct measurements of coronal temperatures above 1.5 solar radii. Data were obtained in a coronal hole, quiet region, and streamer. The widths of the profiles from the quiet region decrease with height and correspond to a steady decrease in hydrogen kinetic temperature, with increasing radius, from about 2.5 x 106 K at rapprox. =2Rsun to about 106 K at rapprox. =4Rsun. In the coronal hole the measured line widths indicate a kinetic temperature of 1.8 x 106 K at rapprox. =2.5 Rsun