Preliminary results from coordinated SOHO-Ulysses observations
AIP Conference Proceedings
SOHO-Ulysses quadratures occur at times when the SOHO-Sun-Ulysses angle is 90° and offer a unique possibility to compare properties of plasma parcels observed in the low corona with properties of the same parcels measured, in due time, in situ. The June 2000 quadrature occurred at a time Ulysses was at 3.35 AU and at a latitude of 58.2 degrees in the south-east quadrant. Here we focus on the UVCS observations made on June 11, 12, 13, 16. UVCS data were acquired at heliocentric altitudes ranging
... c altitudes ranging from 1.6 to 2.2 solar radii, using different grating positions, in order to get a wide wavelength range. The radial direction to Ulysses, throughout the 4 days of observation, traversed a region where high latitude streamers were present. Analysis of the spectra taken by UVCS along this direction shows a variation of the element abundances in the streamers over our observing interval: however, because the radial to Ulysses crosses through different parts of streamers in different days, the variation could be ascribed either to a temporal or to a spatial effect. The oxygen abundance, however, seems to increase at the edge of streamers, as indicated by previous analyses. This suggests the variation may be a function of position within the streamer, rather than a temporal effect. Physical conditions in streamers, as derived from UVCS observations, are also discussed.