Authors: P. Wurz, P. Bochsler, P.A.Paquette, and F.M. Ipavich
Reference: Astrophys. Jou., 583, 489-495, 2003
We report on the calcium abundance in the solar wind for an extended time period around the 1996 solar minimum. Data were recorded with the Mass Time-of-Flight (MTOF) sensor of the Charge, Element, and Isotope Analysis System (CELIAS) instrument on the SOHO spacecraft. The Ca/O abundance is 0.017 +/- 0.003 for slow solar wind (VSW < 400 km s^-1) and 0.0053 +/- 0.0014 for fast solar wind (VSW > 500 km s^-1). Compared to the photospheric Ca/O abundance ratio of (Ca/O)_PS = 0.00421 +/- 0.00079, the solar wind clearly shows strong first ionization potential (FIP) fractionation as is expected for a low-FIP element. The Ca/H abundance is A_Ca = 6.63 +/- 0.05 and A_Ca = 6.21 +/- 0.10 for slow and fast solar winds, respectively. For comparison, the photospheric Ca abundance is A_Ca = 6.36 +/- 0.02.