Other
Scientific paper
May 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm..sh21b07m&link_type=abstract
American Geophysical Union, Spring Meeting 2001, abstract #SH21B-07
Other
2164 Solar Wind Plasma, 2169 Sources Of The Solar Wind, 7511 Coronal Holes, 7536 Solar Activity Cycle (2162), 7549 Ultraviolet Emissions
Scientific paper
A large coronal hole at a latitude of about 60 degrees was observed above the north pole with the Ultraviolet Coronagraph Spectrometer (UVCS) aboard SOHO during 10--19 February 2001. These observations are part of an ongoing campaign to characterize equatorial and mid-latitude coronal holes during the active phase of the current solar cycle. Observations in H~I Lyα and O~VI 103.2 and 103.7 nm provided spectroscopic diagnostics of proton and O5+ velocity distributions. The O~VI line profiles show a narrow core and broad wings. The narrow core is attributed to the foreground and background streamers. The broad wings are attributed to the coronal hole. We compare the observed line intensities and widths of this high-latitude hole with those of other solar maximum (lower latitude) holes and solar minimum polar coronal holes. The comparison of the line widths shows that the O~VI line widths of this solar maximum hole are similar to those observed in polar coronal holes at solar minimum. The observation of extremely high ion kinetic temperatures at the north pole occurs simultaneously with the polarity change of the Sun's magnetic field, as seen in recent magnetogram data. This coronal hole may represent the first manifestation of the stable polar coronal holes that will dominate the Sun's open magnetic flux tubes at the next solar minimum. The re-appearance of broad O~VI profiles at a time when not all of the ``new polarity'' magnetic flux has migrated to the poles is an interesting development that may provide a crucial constraint on models of extended coronal heating. This work is supported by NASA under Grant NAG5-10093 to the Smithsonian Astrophysical Observatory, by the Italian Space Agency and by PRODEX (Swiss contribution).
Cranmer Steven R.
Kohl John L.
Miralles M.
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