Solar wind structure determined by corotating coronal inhomogeneities: 1. Velocity-driven perturbations

Abstract

We extend the previous work on non-spherically symmetric solar wind models, which involved only two independent variables, by deriving the perturabtion equations for the three independent variables, γ, θ, and η, of a spherical polar coordinate system corotating with the sun. The results can be applied to an arbitrary distribution of coronal inhomogeneities with lifetimes long as compared with a flow time of several days and, hence, are restricted to large scale solar wind variations. Two special distributions are given as examples, one north-south symmetric and one north-south antisymmetric; both have four perturbation cycles in one solar rotation. Boundary conditions appropriate to a ‘pure fast-slow stream interaction’ are applied. Comparison with solar wind data suggest that this simple boundary condition can explain occasionally seen structures, but more generally a boundary condition that includes entropy variations is implied.