Working Group 4 Report: Composition and Elemental Abundance Variations in the Solar Atmosphere and Solar Wind |
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Authors: | Helen E Mason Peter Bochsler |
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Institution: | (1) Department of Applied Mathematics and Theoretical Physics, Silver Street, Cambridge, CB3 9EW, UK;(2) Space Physics Group, Department of Physics, University of Maryland, College Park, MD 20742, USA |
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Abstract: | This paper contains a summary of the topics treated in the working group on abundance variations in the solar atmosphere and
in the solar wind. The FIP bias (overabundance of particles with low First Ionization Potentials over photospheric abundances)
in coronal holes and coronal hole associated solar wind amounts to values between 1 and 2. The FIP bias in the slow solar
wind is typically a factor 4, consistent with optical observations in streamers. In order to distinguish between different
theoretical models which make an attempt to explain the FIP bias, some observable parameters must be provided. Unfortunately,
many models are deficient in this respect. In addition to FIP fractionation, gravitational settling of heavy elements has
been found in the core of long lived streamers. The so-called electron 'freeze in' temperatures derived from in situ observed
ionization states of minor ions in the fast wind are significantly higher than the electron temperatures derived from diagnostic
line ratios observed in polar coronal holes. The distinction between conditions in plumes and interplume lanes needs to be
further investigated. The 'freeze in' temperatures for the slow solar wind are consistent with the electron temperatures derived
for streamers.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | element abundances in situ observations UV data |
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