Working group 4 report: Composition and elemental abundance variations in the solar atmosphere and solar wind

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 FL P bias (overabundance of particles with low First Ionization Potentials ove r photospheric abundances) in coronal holes and coronal hole associated sol ar wind amounts to values between 1 and 2. The FIP bias in the slow solar w ind is typically a factor 4, consistent with optical observations in stream ers. In order to distinguish between different theoretical models which mak e an attempt to explain the FLP bias, some observable parameters must be pr ovided. Unfortunately, many models are deficient in this respect. In additi on to FLP fractionation, gravitational settling of heavy elements has been found in the core of long lived streamers. The so-called electron 'freeze i n' temperatures derived from in situ observed ionization states of minor io ns in the fast wind are significantly higher than the electron temperatures derived from diagnostic line ratios observed in polar coronal holes. The d istinction between conditions in plumes and interplume lanes needs to be fu rther investigated. The 'freeze in' temperatures for the slow solar wind ar e consistent with the electron temperatures derived for streamers.