EGS, 23rd General Assembly, Nice, 20-24 April 1998
Abstract:
During 1992 and 1993 the Ulysses spacecraft observed a long sequence of
Corotating Interaction Regions (CIRs) produced by the interaction of high
speed solar wind from the south polar coronal hole with slow speed wind
from the near equatorial streamer belt. Stream interfaces in the CIRs
separate the plasmas that originated in low speed solar wind and high speed
solar wind at their source in the corona, while the heliospheric current
sheet (HCS) separates magnetic fields of opposite polarity. In this paper
we examine and classify the behaviour of the magnetic field in the vicinity
of the HCS crossings and the stream interfaces during the above sequence of
CIRs. A variety of HCS crossing signatures are found, some a clean
discontinuity between the opposite polarities, others where the crossing is
replaced by an apparent flux rope like signature. In some, but not all,
cases we find clear magnetic field discontinuities also at the stream
interface, although often these don't appear very different from other
discontinuities elsewhere in the CIR. The results of this study are of
importance in understanding which features within CIRs play a role in the
modulation of energetic particle signatures.