The solar wind is considered as a steady fully ionized hydrogen plasma flow, with rotational symmetry. The Parker-spiral type magnetic field specifies the dependence of the flow speed on the radial distance and meridional angle if the plasma is assumed to be quasi-neutral and currentless. A two-particle kinetic model of the collisionless rotationally symmetrical plasma flow in a magnetic field is formulated and applied to estimate the flux and density of the solar wind. The obtained theoretical results are compared to the observational data.