SOLAR AND HELIOSPHERIC PROCESSES FROM SOLAR-WIND COMPOSITION MEASUREMENTS

Composition measurements in the solar wind provide important informati on for solar system science and astrophysics. We show in this report h ow ion composition data are used to investigate chromospheric and coro nal processes. Isotopic abundances in the Sun can best be derived from solar wind measurements. He-3/He-4 is an isotopic ratio with far-reac hing implications. It allows us to determine the deuterium abundance i n the proto-solar nebula, which in turn leads to an estimate of deuter ium production in the early universe. The interstellar gas is the seco nd most important source of heliospheric ions. Atomic abundances in th e local interstellar gas are derived from ion composition measurements , and processes in the solar wind termination region and beyond are st udied.