Meeting abstract

31st ESLAB Symposium, ESTEC, The Netherlands, 22-25 September 1997

Abstract:
Corotating Interaction Regions (CIRs) are the dominant feature of the near-equatorial regions of the heliosphere around solar minimum. Ulysses observations discussed in this paper cover the declining phase of Solar Cycle 20 in 1992-93 up to southerly mid-latitudes. These observations have provided the basis for the study of the latitudinal extent of CIRs and their evolution. We relate the evolution of coronal holes and the position of the magnetic neutral line during this declining phase of the cycle to the observed properties of CIRs at Ulysses. We examine in detail the CIRs observed by Ulysses; these CIRs present in fact a complex picture of multiple compressive regions associated with each CIR. This results from a dynamic interplay between the solar sources of high speed solar winds and their evolution in the heliosphere. The mismatch between the interplanetary observations and the observed coronal structures is interpreted in terms of the three-dimensional dynamics of the CIRs and their interaction with the heliospheric current sheet.