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H.P. Warren (SAO)
Recent observations of Doppler shifts with the SUMER spectrometer on SoHO have shown that there is a transition from net redshifts (apparent inflows) to blueshifts (outflows) at approximately 630,000 K in solar coronal holes. These outflows appear to be directly related to the formation of the high speed solar wind. This transition from net redshifts to blueshifts is significant because it supports the idea that much of the solar transition region is not connected to the corona, but is confined on small, closed loops. Measurements of elemental abundances hold important clues to the structure of solar corona and the origin of the high speed solar wind. In situ measurements of the high speed solar wind indicate that low first ionization potential elements are enriched by about a factor of two or less over their photospheric values. The slow speed wind, which is formed from quiet regions, shows much larger enrichements. Skylab-era measurements of emission formed in the lower transition region suggested no enrichment of low FIP elements at these temperatures in either the quiet Sun or coronal holes. In this paper we present a systematic investigation of abundance variations as a function of temperature in the quiet Sun and coronal holes using observations from the SUMER and CDS spectrometers on SoHO. We also discuss the relationship between abundance variations and the morphology of the solar atmosphere using high resolution images from TRACE.
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