Meeting abstract

IAGA, 8th Scientific Assembly, Uppsala, Sweden, 4-8 August, 1997

Abstract:
Corotating Interaction Regions (CIRs) are the dominant feature of the near-equatorial regions of the heliosphere around solar minimum. Ulysses observations of CIRs cover three intervals during the declining phase of Solar Cycle 20 and the start of Cycle 21: in 1992-93 up to southerly mid-latitudes, in 1994-95 a fast scan in latitude from south to north and in 1996-97 at mid- and low latitudes. These observations have provided the basis for the study of the latitudinal extent of CIRs and their evolution at different phases of the solar cycle. This paper reviews the results from the earlier periods, and discusses in detail the observations made during the most recent period. As solar activity increases from minimum, the evolution of coronal holes, in particular any longitudinal and latitudinal asymmetries in their pattern on the sun strongly affect the development and latitudinal extension of CIRs. We examine the CIRs observed by Ulysses and relate them to their solar origins. The mismatch between the interplanetary observations and the observed coronal structures is interpreted in terms of the three- dimensional dynamics of the CIRs in the heliosphere.