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arXiv · 1508.04566

Variations in solar wind fractionation as seen by ACE/SWICS over a solar cycle and the implications for Genesis Mission results

P. Pilleri·D. B. Reisenfeld·T. H. Zurbuchen·S. T. Lepri·P. Shearer·J. A. Gilbert·R. von Steiger·R. C. Wiens
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Abstract

We use ACE/SWICS elemental composition data to compare the variations in solar wind fractionation as measured by SWICS during the last solar maximum (1999-2001), the solar minimum (2006-2009) and the period in which the Genesis spacecraft was collecting solar wind (late 2001 - early 2004). We differentiate our analysis in terms of solar wind regimes (i.e. originating from interstream or coronal hole flows, or coronal mass ejecta). Abundances are normalized to the low-FIP ion magnesium to uncover correlations that are not apparent when normalizing to high-FIP ions. We find that relative to magnesium, the other low-FIP elements are measurably fractionated, but the degree of fractionation does not vary significantly over the solar cycle. For the high-FIP ions, variation in fractionation over the solar cycle is significant: greatest for Ne/Mg and C/Mg, less so for O/Mg, and the least for He/Mg. When abundance ratios are examined as a function of solar wind speed, we find a strong correlation, with the remarkable observation that the degree of fractionation follows a mass-dependent trend. We discuss the implications for correcting the Genesis sample return results to photospheric abundances.

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P. Pilleri, D. B. Reisenfeld, T. H. Zurbuchen, S. T. Lepri, P. Shearer, J. A. Gilbert, R. von Steiger, R. C. Wiens. 2015-08-19. Variations in solar wind fractionation as seen by ACE/SWICS over a solar cycle and the implications for Genesis Mission results. https://doi.org/10.1088/0004-637x%2F812%2F1%2F1

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