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Paper: Time Evolution of a Coronal Velocity Source Surface during Solar Cycle 23
Volume: 428, SOHO-23: Understanding a Peculiar Solar Minimum
Page: 187
Authors: Strachan, L.; Panasyuk, A. V.; Kohl, J. L.
Abstract: We present preliminary results of a study to create coronal outflow velocity maps for the period from 1996 to 2005. The velocities are derived from the UVCS/SOHO synoptic observations of the O VI 103.2 nm and 103.7 nm intensities. The maps are made at a constant heliocentric height of 2.3 Rsun, near the traditional coronal source surface height of 2.5 Rsun. Our results for the Cycle 22/23 minimum show that the classic solar minimum conditions, where high-speed wind dominates the polar regions, lasted only until May 1997. However, during the same time period there was very little change in the fraction of fast or slow speed wind at low heliographic latitudes (< 30°). When completed, the coronal velocity maps will be used to show the connections between structures in the corona and solar wind streams at greater distances from the Sun. It will also help clarify how variations in the spatial distribution of outflow velocities are controlled by the coronal magnetic field and plasma conditions at the source regions.
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