EVOLUTION OF INTERPLANETARY FLOW VELOCITY ENHANCEMENT DISTURBANCE
行星际速度增幅扰动的演化

Using an ideal two-dimensional MHD model, this paper investigates the evolution of a pure flow velocity enhancement disturbance in the solar wind in the heliospheric equatorial plane (2-D, 2-component model) and the heliospheric meridional plane (2-D, 3-component model). It is shown that the disturbance evolves into a double shock pair, i.e., a shock system that consists of four shocks: a reverse fast shock, a reverse slow shock, a forward slow shock, and a forward fast shock from the close to the distant with respect to the Sun. The double shock pair is nearly symmetrical with respect to the central normal of the disturbance source in the heliospheric meridional plane, whereas it is asymmetrical in the heliospheric equatorial plane. On the western side of the central normal of the disturbance source in the heliospheric equatorial plane, the double shock pair structure is more evident, and the longitudinal span is wider than those on the eastern side. A preliminary analysis shows that the east-west asymmetry in the heliospheric equatorial plane is mainly attributed to the spiral structure of the interplanetary magnetic field.