MHD analysis of the velocity oscillations in the outer heliosphere

We carried out a MHD simulation of deep interplanetary space from 2001 to 2009 with a realistic inner boundary condition obtained from a time‐dependent 3‐D ideal MHD model incorporating interplanetary scintillation and synoptic solar magnetic field data. As a result, we found that wavy solar wind structure with amplitudes of 10–50 km/s and a monochromatic wavelength of ~2 AU filled deep interplanetary space beyond ~50 AU from the Sun, which corresponds to a velocity oscillation detected by Voyager 2. The phase of the velocity oscillation is anticorrelated with density fluctuations in our simulation, which suggests that the velocity oscillation should propagate inward toward the Sun in the frame moving with the solar wind but is advected outward by the solar wind in the rest frame of the Sun.