The May 1997 SOHO-Ulysses quadrature

Abstract

We present results from the May 1997 SOHO-Ulysses quadrature (SOHO-Sun-Ulysses angle=90°), near sunspot minimum. Ulysses was at 5.1 AU, 10° north of the solar equator, and off the east limb. It was also at the very northern edge of the streamer belt. Nevertheless, the Solar Wind Observations Over the Poles of the Sun instrument (SWOOPS) detected only slow, unusually smooth wind and there was no direct evidence of fast wind from the northern polar coronal hole or of mixing with fast wind. The Large-Angle and Spectrometric Coronagraph (LASCO) images show that the streamer belt at 10° N was narrow and sharp at the beginning and end of the 2 week observation interval, but broadened in the middle. A related change in density, but not flow speed, occurred at Ulysses. Under these conditions it was possible to show that densities derived from the Ultraviolet Coronagraph Spectrometer (UVCS) in the lower corona are closely related to those in the solar wind, both over quiet intervals and in transient events on the limb. Density and velocity in one small transient observed by both LASCO and UVCS are analyzed in detail. Copyright 2000 by the American Geophysical Union.