Craig DeForest (Stanford University); Barbara Bromage, Giulio Del Zanna (University of Central Lancashire); Don M Hassler (Southwest Research); Barbara Thompson (NASA GSFC/Applied Research Corp.)
Equator-crossing solar coronal holes afford a rare opportunity to view the source region of high-speed solar wind from a nearly vertical vantage. During SoHO's "Whole Sun Month" observing campaign of August 1996, a large equator-crossing coronal hole extension (the "Elephant's Trunk") was visible on the solar disk. XUV emission-line movies recorded by EIT during that time show the coronal hole extension as a deep, narrow canyon between high walls of quiescent corona; spectra recorded by CDS and by SUMER have been used to determine plasma diagnostic information about the hole, its boundary, and the and the surrounding quiet corona; and MDI's magnetogram program shows strong magnetic features associated with the elephant's trunk. We present detailed information on the morphology and evolution of the coronal hole extension as it crossed the disk; estimate and compare the temperature and electron density inside and outside the coronal hole; and search for a magnetic signature of the coronal hole boundary.
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