The composition of the solar wind

Abstract

Accurate knowledge of the composition of the solar wind and of solar system abundances allows us to improve our understanding about various processes affecting the elemental, isotopic, and charge-state abundances of the solar wind. During the evolution of the Sun, isotopic and elemental abundances have been affected by migration processes at the interface between the well mixed outer convective zone and the radiative zone. In the solar atmosphere, the isotopic and elemental composition can be affected by Coulomb drag and wave-particle interactions. In addition, elemental abundances are clearly fractionated by some process that is controlled by the first ionization potential (FIP) of the elements. The abundances of the charge states are determined by processes in the corona, and, in interplanetary space, serve as valuable tracers for the coronal origin of the solar wind. The abundances of certain key elements and their isotopes can safely and accurately be determined from their meteoritic values. Their abundances in the solar wind can be used to obtain estimates for the degree of fractionation undergone by other elements and their isotopes, for which the meteoritic abundances do not necessarily reflect photospheric values, or for which it is not clear which meteoritic component corresponds to solar values. In short, the composition of the solar wind can yield valuable information about processes in the early solar system and its evolution, the evolution of the Sun, processes in the solar interior, atmosphere, and corona, as well as in interplanetary space.