On the detection of heliospheric interface properties from interstellar/interplanetary Lyman-alpha profiles - Example of Baranov's two-shock model
Résumé
Interstellar/interplanetary neutral H atoms which are observed towards the upwind (UW) and downwind (DW) directions do not originate from the same region of the heliospheric interface. If the neutral/plasma coupling is not negligible, the variations of the plasma properties with the distance to the stagnation line are imprinted in the neutral atoms and in the relationship between the UW and DW Lyman-alpha spectral profiles, whatever the distance to the heliospheric shock and to the heliopause. This effect is checked both on the Prognoz 5/6 backscattered Lyman-alpha data and in the case of the Baranov type interface. Hydrogen absorption cell data interpretation is much improved when inhomogeneities of the interstellar wind are taken into account. Lyman-alpha profiles derived from the Monte Carlo neutral flow model of Malama (1990) show the predicted macroscopic effects. These results tend to show that information on the type of the interface at the heliopause can be derived from precise Lyman-alpha line shape measurements and from comparison with line shapes computed from a homogeneous interstellar flow model.