Dynamic processes in the outer heliosphere: voyager observations and models

We review recent Voyager 2 observations in the vicinity of 70 AU. The character of the solar wind plasma data between 2002 and 2003 changed to a regime in which the speed, density and magnetic field magnitude are positively correlated. The average speed of the solar wind at Voyager 2 increased between early 2003 and mid-2004, which we attribute to a return of fast coronal hole flow. We use solar wind data at Earth as input to numerical models which include the effect of pickup ions to model the radial evolution of the solar wind. The model reproduces the basic features of the observations. As a specific example, we investigate the propagation of the Halloween (Oct.–Nov.), 2003 storms in the outer heliosphere. The model predictions are in reasonable agreement with Voyager 2 observations.