Sulfur Abundance in the Slow Solar Wind

Using 4 years of data from the Mass Time-of-Flight and Proton Monitor, two CELIAS sensors on board SOHO, we report the sulfur abundances in comparison to magnesium and calcium (two low first ionization potential elements) for the slow solar wind, and for the first time we measure the sulfur isotopic abundance ratio. For the period in which the proton velocity was 380 ± 2 km s-1 we obtain [S]/[Mg] = 0.26 ± 0.03, [S]/[Ca] = 4.7 ± 0.5, and [34S]/[S] = 0.043 ± 0.009. We compare these measurements with the available measurements reported in the literature, and we check the quality of the results by using the magnesium isotopic ratio and the calcium-to-magnesium abundance ratio as a control. Finally, as a further result we also obtain the absolute abundance of the previous elements. In astronomical notation we have AS = 7.44 ± 0.04, AMg = 8.03 ± 0.05, and ACa = 6.77 ± 0.04.