Paper presented at the 5th SOHO Workshop, 17-20 June, 1997, Oslo, Norway
Solar wind particles can be used as tracers for a wide variety of heliospheric processes. The FIP effect "paints" the solar wind at its source, giving different colours in the form of chemical abundances to different stream types, such as coronal hole associated streams or low-speed interstream solar wind. The charge state of minor elements is established in the corona at distances from 1 R0 to several R0 and remains frozen thereafter on its way out into space. Depending on the flux tube geometry and on the efficiency of Coulomb friction near the critical point, helium is more or less strongly depleted relative to hydrogen and most of the other elements. Correspondingly, we expect isotopic fractionation effects of the order of a few percent per mass unit to occur in the interstream solar wind whereas virtually no depletion of heavy isotopes is expected in the high speed solar wind. The dynamic properties (bulk speed, kinetic temperature, density) of solar wind ions can be modified by various processes from the innermost regions of the corona out to the fringes of the heliosphere. The so-called pick-up ions are generated in the interplanetary medium and incorporated into the solar wind due to charge exchange of interstellar neutrals with solar wind ions or by solar EUV-radiation. This population provides clues about the composition and the dynamics of the local interstellar medium.