The Relative Abundance of Chromium and Iron in the Solar Wind as Measured With SOHO/CELIAS/MTOF
Abstract
Measurements are presented of the abundance ratio of chromium to iron in the solar wind in various flow types, and also for several approximately 1-year long intervals in restricted speed ranges. The mass discrimination of the MTOF (Mass Time-Of-Flight) sensor of the CELIAS investigation on the SOHO spacecraft easily allows solar wind chromium and iron to be resolved from each other, despite the similarity in these two elements' masses (Chromium's most common isotope is mass 52, while the most common isotope of iron is mass 56). Taking the ratio of the densities of these two elements - as opposed to considering their absolute abundances - minimizes the effects of uncertainties in instrument efficiency. The First Ionization Potential (FIP) of Chromium is 6.76 eV, while the FIP of Iron is 7.87 eV. Since Cr and Fe both have low FIPs the ratio of their abundances should not be biased by the FIP effect which is well known in different solar wind flows. Therefore the Cr/Fe ratio from the MTOF data should give a good measure of the photospheric abundance ratio. We also compare the ratio measured in this work to the meteoritic value. Use is made of the MTOF sensor's retarding potential to extend the study to higher solar wind speed regimes than in previous work. A more realistic estimate of the solar wind charge states (taken from Mazzotta et al) is also used.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2002
- Bibcode:
- 2002AGUSMSH21C..08P
- Keywords:
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- 2164 Solar wind plasma;
- 2169 Sources of the solar wind