Temporal Evolution of Solar Wind Ion Composition and Their Source Coronal Holes During the Declining Phase of Cycle 23. I. Low-Latitude Extension of Polar Coronal Holes

摘要: We analyzed 27 solar wind (SW) intervals during the declining phase of cycle 23, whose source coronal holes (CHs) can be unambiguously identified and are associated with one polar CHs. found that SW ions have a temporal trend decreasing ionization state, such is different between slow fast SW. The photospheric magnetic field, both inside at outside boundary CH, also exhibits decrease time. However, EUV line emissions from layers atmosphere exhibit trends. emission CH generally increases toward as underlying field in strength becomes less unipolar. In contrast, this relationship not seen averaged over entire CH. For C O freeze-in lower altitude, stronger correlation their states (both signed unsigned) appears SW, while for Fe higher Such correlations its region. On other hand, electron temperature correlates well ion composition only Our analyses, although able to determine likely footpoint locations speeds, raise many outstanding questions how heated accelerated response long-term evolution field.