Oxygen flux in the solar wind: Ulysses observations

Abstract

We use the complete set of Ulysses solar wind data to conduct a comprehensive determination of the oxygen flux in relation to the proton flux in the solar wind during a wide range of solar activity levels. The data cover the heliosphere between 1.3 and 5.4 AU and, due to the unique orbit of Ulysses, all of the heliographic latitudes within ±80°. We find log-normal distributions for O and H daily flux values, but with significant differences between slow and fast wind. Coronal hole-associated fast wind has a distribution that is approximately three times narrower than the one of slow wind associated with streamers. Finally, we derive the solar oxygen abundance, finding a value of 8.82 ± 0.08, and discuss this value in comparison with the results of spectroscopic determinations.