THE FALL 2001 POLAR SOHO-ULYSSES QUADRATURE CAMPAIGN: PRELIMINARY RESULTS

摘要

We present here UVCS observations of a polar coronal hole, acquired during the October/November 2001 SOHO-Sun-Ulysses quadrature. SOHO-Ulysses quadratures occur when the SOHO-Sun-Ulysses included angle is 90° and offer the unique opportunity of comparing the properties of plasma parcels, observed by SOHO in the corona, with properties of the same parcels, measured in situ, in due time, by Ulysses. The October/November 2001 quadrature occurred at a time when Ulysses was at ≈ 2.2 A.U., at a northern heliographic latitude of ≈ 80°, off the West limb of the Sun. Observations were taken from October 29 to November 12, 2001, with a ≈ 3 days data gap, after the eruption of CMEs and the emission of highly energetic particles, on 3-4 November. The UVCS slit was set normal to the solar radius, with the radial to Ulysses going through its zero position. At the time of the campaign, the radial to Ulysses crossed a polar coronal hole. Although its shape was changing, Ulysses was permanently located in a high speed region where CMEs signature can be recognized. Observations in Hydrogen Lyman-α and in the 1032 and 1037 A O Ⅵ doublet lines have been made at 1.6 and 2 solar radius. Line intensities are compared with intensities typically found, at the same altitudes, in polar coronal holes at minimum solar activity and in equatorial holes. The temporal profile of the O Ⅵ doublet line ratio and of the O Ⅵ line widths, at the position where the radial to Ulysses traverses the solar corona, are shown and a tentative interpretation of the data is outlined.