Spectral properties of backscattered solar Ly-alpha radiation in the heliosphere: a theoretical search of the heliospheric boundaries effects

摘要

We explore imprints of the solar wind interaction with the local interstellarmedium on spectral properties of the backscattered solar Ly-alpha radiation. Weemploy newly developed effective model for the interstellar H atom velocitydistribution function in the heliosphere (Katushkina and Izmodenov 2010, 2011).This model takes into account both global effects of H atom perturbations atthe heliospheric boundaries and local (i.e. within 10-20 AU from the Sun)effects of the solar ionization, charge exchange, solar gravitation andradiation pressure. Backscattered solar Ly-alpha profiles and their zero, firstand second moments were computed at 1 AU for the anti-solar directions ofline-of-sight. Then the moments are compared with the moments calculated byusing more simplified one-component and two-component hot models. Thecomparison shows that the Ly-alpha intensities calculated in the frame of newmodel are somewhat smaller than those calculated by means of the simplifiedmodels. Small differences in the first moment (i.e. line-shift) are alsoobserved in the downwind direction. The largest difference between new modeland hot models is seen in the second moment of the backscattered Ly-alphaprofile. This moment is also called as line-of-sight temperature or line-widthof the backscattered spectra. The spectral width depends on the width of the Hatom velocity distribution function within few AU from the Sun. We show thatthe line-widths calculated on the basis of the our model is qualitativelydifferent from those of simplified models.