A new estimate of interstellar helium parameters from measurements of Voyager 1/2 ultraviolet spectrometers

Measurements of the He I 58.4 nm interplanetary emisson collected by the UVS on board Voyager 1 and 2 were reduced and compared to a computer code model. This model predicts the distribution in the solar system of interstellar helim atoms at temperature T, flowing at velocity V and predicts also the emission by resoncance scattering of He I 58.4 nm solar photons. It is shown in the present study that the emissivity pattern of helim atoms illuminated by the sun can be well represented by several combinations of parameters (temperature, velocity, solar line width). The comparison of Voyager results and previous estimates of the helim temperatures leads to a temperature of 12000±2000K and a velocity of 24.5±0.5 km s^-1.