Dynamical evolution of the inner heliosphere approaching solar activity maximum: interpreting Ulysses observations using a global MHD model

Abstract. In this study we describe a series of MHD simulations covering the time period from 12 January 1999 to 19 September 2001 (Carrington Rotation 1945 to 1980). This interval coincided with: (1) the Sun’s approach toward solar maximum; and (2) Ulysses’ second descent to the southern polar regions, rapid latitude scan, and arrival into the northern polar regions. We focus on the evolution of several key parameters during this time, including the photospheric magnetic field, the computed coronal hole boundaries, the computed velocity profile near the Sun, and the plasma and magnetic field parameters at the location of Ulysses. The model results provide a global context for interpreting the often complex in situ measurements. We also present a heuristic explanation of stream dynamics to describe the morphology of interaction regions at solar maximum and contrast it with the picture that resulted from Ulysses’ first orbit, which occurred during more quiescent solar conditions. The simulation results described here are available at: http://sun.saic.com.

Key words. Interplanetary physics (Interplanetary magnetic fields; solar wind plasma; sources of the solar wind)