Determination of the abundance of aluminum in the solar wind with SOHO/CELIAS/MTOF

The Al/Mg abundance ratio provides an excellent test case for investigating possible fractionation processes among low First Ionization Potential (FIP ) elements in the solar wind. Al and Mg are refractory elements; their abun dance ratio has been well determined in solar system materials and inferenc es for the abundance ratio in the solar atmosphere are reliable. Al and Mg are at neighboring masses and have similar charge state properties in the s olar corona; hence mass fractionation effects in the solar wind acceleratio n process and instrumental mass fractionation are minimal. From first obser vations during two relatively short periods, one recorded in coronal hole a ssociated solar wind, the other in typical interstream solar wind, it is co ncluded that the solar wind ratio in both regimes is consistent with the so lar system ratio. The Al/Mg ratio in interstream solar wind is 0.081+/-0.01 2, and in the sample of coronal hole associated solar wind it amounts to 0. 076+/-0.011. A comparison of these results with the solar system ratio of 0 .079+/-0.005 gives no indication for fractionation occurring among low FIP elements in the solar wind.