A reference frame in the solar wind can often be found wherein the flow vector is everywhere approximately parallel to the magnetic-field vector . This is the frame of the heliospheric magnetic structure moving relative to the plasma. Since v perpendicular is very small in this reference frame, the magnetic structure appears to have little temporal evolution. The structure moves outward away from the Sun faster than the plasma flow. Even for highly Alfvénic plasma, the structure does not move at the Alfvén speed relative to the proton plasma, rather it moves at ~0.7vA. The degree of inhomogeneity of the plasma is hypothesized to control the motion of the magnetic structure through the plasma. If so, non-Alfvénicity may be owed to an inability of Alfvénic perturbations to coherently propagate from Alfvénic injections at the Sun. Schemes that mathematically advect magnetic and plasma structure from upstream-solar-wind monitors to the Earth may be improvable by calculating and including the motion of the structure relative to the solar-wind velocity vector.