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K. L. Harvey (SPRC), F. Recely (SEC/NOAA)
Coronal holes are studied to investigate their variation over a solar cycle. We use the NSO/Kitt Peak synoptic Carrington rotation maps of He I 10830 nm and magnetic fields to identify coronal holes and measure their position, area, boundaries, and magnetic flux as a function of time. Our study covers a period from February 1975 to the present (March 1999). This 25-year interval includes three minima, at the onset of cycles 21, 22, and 23, and two maxima, that of cycles 21 and 22. We will present results on the temporal variation in area and magnetic flux separating the identified coronal holes into two types, polar and lower-latitude, isolated holes, and how these parameters relate temporally and spatially to solar activity. We will also consider differences in the variation of coronal holes between the northern and southern hemispheres. This research is funded through NSF Grant ATM-9713576.
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