Absolute redshifts in the C iv 1548 � line in the transition region of the quiet Sun

Abstract

Observations with the UVSP instrument on the SMM spacecraft were made at the polar limb and disk center for the accurate determination of Doppler shifts of the Civ 1548 A emission line formed at 105 K in the transition region of the quiet Sun. Individual data points representing 3 arc sec square pixels yield both redshifts and blueshifts, but the mean values from four different days of observations are toward the red. The mean redshifts are in the range 4–8 km s-1 and are produced by nearly vertically directed flows; the uncertainty associated with the mean values correspond to ±0.5 km s-1. The redshift increases with brightness of the Civ line.