ELEMENTAL ABUNDANCES IN THE FAST SOLAR WIND EMANATING FROM CHROMOSPHERIC FUNNELS

Author
Pucci, Stefano
Lie-Svendsen, Øystein
Esser, Ruth
Date Issued
2010
Keywords
TermsetEmneord::Ionisering
TermsetEmneord::Vind
TermsetEmneord::Strømning
Permalink
http://publications.ffi.no/handle/123456789/432
DOI
10.1088/0004-637X/709/2/993
Collection
Articles
Description
Pucci, Stefano; Lie-Svendsen, Øystein; Esser, Ruth. ELEMENTAL ABUNDANCES IN THE FAST SOLAR WIND EMANATING FROM CHROMOSPHERIC FUNNELS. The Astrophysical Journal 2010 ;Volum 709.(2) s. 993-1002
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Abstract
We carry out a model study to determine whether a funnel-type flow geometry in the solar wind source region leads to sufficiently fast hydrogen flow to offset heavy element gravitational settling and can thus explain why solar wind abundances are not much smaller than photospheric abundances. We find that high first ionization potential (FIP) elements are more susceptible to gravitational settling than low-FIP elements, which are pulled up by Coulomb drag from protons, and hence the settling is more sensitive to the charge state of the elements than to their mass. Abundances at the top of the chromosphere, and hence solar wind abundances, can change by many orders of magnitude when the funnel areal expansion factor is changed by a small amount. The observed solar wind neon abundance provides the most severe constraint on the expansion, requiring a total flux tube expansion factor of at least 30-40.
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