Physics
Scientific paper
Jun 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002esasp.508..351m&link_type=abstract
In: Proceedings of the SOHO 11 Symposium on From Solar Min to Max: Half a Solar Cycle with SOHO, 11-15 March 2002, Davos, Switze
Physics
8
Coronal Holes, Solar Corona, Solar Wind, Uv Spectroscopy
Scientific paper
UVCS/SOHO has been used to measure the plasma properties of several types of coronal holes from 1996 to early 2002 at heights from 1.5 to 3.5 Rsolar. UVCS observations show a variation in ion properties between coronal holes from solar minimum to solar maximum. Different coronal holes seem to exhibit different heating and acceleration rates. Polar coronal holes at solar minimum exhibited the most extreme ion properties with O5+ perpendicular temperatures in excess of 2×108K, O5+ outflow speeds of at least 400 km/s by 3 Rsolar, and the lowest densities. Equatorial coronal holes at solar maximum exhibited the least extreme ion plasma properties with O5+ perpendicular temperatures less than 8×107K, O5+ outflow speeds of only 100 km/s by 3 Rsolar, and the largest densities. However, large polar and equatorial coronal holes produce interplanetary wind streams with similar speeds (v ~ 700 km/s). Thus, most of the solar wind acceleration in large equatorial coronal holes must occur above 3 Rsolar. The first high-latitude coronal hole of the new negative magnetic polarity observed at the north in 2001 exhibited extreme properties similar to those of the 1996 - 1997 polar coronal holes, even though it was 6 years prior to the next minimum. During 2001 - 2002, we have observed mid-latitude coronal holes, with properties in between large polar and equatorial coronal holes.
Cranmer Steven R.
Kohl John L.
Miralles Mari Paz
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