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E. Buchlin (ENS/Paris), D.M. Hassler (SwRI)
SUMER observations have provided new insight into the structure of the source region of the solar wind, and its relationship to the chromospheric magnetic network. Specifically, velocity maps in Ne VIII, formed at the base of the corona, show a relationship between outflow velocity and the underlying network structure (Hassler et al., Science, 1999). However, the time cadence of these observations had to be increased to tell whether these velocity signatures correspond to steady state or transient flows. We present two new observing campaigns that we have organized and performed in 1999 (March 8 and November 3-8) to address this outstanding question while preserving sufficient FOV, involving observations from SOHO (SUMER, EIT, MDI, CDS), TRACE and Kitt Peak. Preliminary analysis of the observations from March 8, 1999 suggest that the majority of the observed flows in both the south polar coronal hole and the equatorial quiet Sun region are relatively quiescent (or slowly evolving) on the time scale of the SUMER observations of 2 hours. However, one significant high speed transient flow (20-30 km/s) was identified in a SUMER scan at the south polar coronal hole, and corresponds to an explosive event or jet observed by TRACE in Fe IX/X 171 which lasted less than an hour. During the November campaign, extensive, coordinated observations were made of an equatorial coronal hole which began on the East limb and rotated across the MDI high resolution FOV at central meridian. Complete coronal hole scans (5 to 9 hours long), several series of three 2-hour long scans and time series with 1 min cadence were made. Intensity, line-of-sight velocity, and line width maps will be presented for emission lines formed at three different heights in the solar atmosphere (Si II 1533, C IV 1548, and Ne VIII 770). This work has been funded in part by NASA under grant NAG5-7815 to Southwest Research Institute.