SOLAR AND HELIOSPHERIC PROCESSES FROM SOLAR-WIND COMPOSITION MEASUREMENTS

Composition measurements in the solar wind provide important information for solar system science and astrophysics. We show in this report how ion composition data are used to investigate chromospheric and coronal processes. Isotopic abundances in the Sun can best be derived from solar wind measurements. He-3/He-4 is an isotopic ratio with far-reaching implications. It allows us to determine the deuterium abundance in the proto-solar nebula, which in turn leads to an estimate of deuterium production in the early universe. The interstellar gas is the second most important source of heliospheric ions. Atomic abundances in the local interstellar gas are derived from ion composition measurements, and processes in the solar wind termination region and beyond are studied.