A Transition to Fast Flows and Its Effects on the Magnetic Fields and Cosmic Rays Observed byVoyager 2near 70 AU

A shocklike transition at 2003.37 from quasi-periodic flows to increasingly fast flows was observed by Voyager 2 (V2) near 70 AU. The transition was related to the appearance of coronal holes near the solar equatorial plane on Carrington rotation (CR) ≈1994. Several important features (two cycles of quasi-periodic variations in V and B, a shock, a merged interaction region (MIR) with strong magnetic fields in a region with increasing speed, and a second shock that was related to the 2003 October 29-30 events at 1 AU) were observed by V2 from 2002.8 to 2004.4. A one-dimensional multifluid MHD model shows that these features at V2 evolved from the flows observed by ACE at 1 AU. The model also shows that the features propagated through the heliosphere out to 95 AU. The changes in the magnetic field associated with the features at V2 caused changes in the cosmic-ray intensity (CRI) of particles more energetic than 70 MeV nucleon-1. The quasi-periodic variations were related to variations in CRI, but they produced no appreciable net decrease in the CRI. Both the first shock and the MIR produced a steplike decrease in the CRI at V2.