The influence of fluctuations of the solar emission line profile on the Doppler shift of interplanetary HLy alpha lines observed by the Hubble-Space-Telescope

In an earlier research the employment of a radiation transport model with a ngle-dependent partial frequency redistribution, self-absorption by interpl anetary hydrogen, realistic solar H-Ly alpha emission profile, and a time d ependent 'hot' hydrogen model to analyze 5 interplanetary H-Ly alpha glow s pectra obtained with the Hubble-Space-Telescope-GHRS spectrometer, has not resulted in unequivocal determination of a set of thermodynamical parameter s of the interstellar hydrogen The residual discrepancies between the model and the data concern the observations performed within an interval of 1 ye ar close to the solar minimum from very similar lines of sight. In this pap er we investigate by calculating interplanetary H-Ly alpha lines with the u se of a one hydrogen distribution and several solar H-Ly alpha line profile s whether this residual may be caused by possible variations in time of the shape of the solar H-Ly alpha emission line profile which cause variable i lluminations of the interplanetary gas. These variations of illuminations c ause variations in Doppler shift of the resonant interplanetary H-Ly alpha line that can amount to similar or equal to 4 km s(-1) in the line peak. Co nsequently we conclude that without adequate knowledge of the solar H-Ly al pha emission line profile during spectral observations of the interplanetar y hydrogen gas it is impossible to obtain an agreement between models and o bservations better than by this value.