U. Feldman et al., Coronal composition above the solar equator and the north pole as determined from spectra acquired by the SUMER instrument on Soho, ASTROPHYS J, 505(2), 1998, pp. 999-1006
Using spectra obtained by the SUMER instrument on the Solar and Heliospheri
c Observatory (SONO) we have determined the composition of the bulk of the
coronal plasma in the vicinity of the solar surface over a polar coronal ho
le and an equatorial region. Our measurements show that although low first
ionization potential (FIP) elements are enriched by about a factor of 4 in
the corona above the quiet equatorial region, little or no enrichment exist
s above the north polar coronal hole. These observations are in good agreem
ent with the Ulysses in situ observations in both fast speed and slow speed
winds.