Mathematical model of the polar wind

The singularities and critical points of the polar-wind equations in the hydrodynamic model of Banks and Holzer are discussed. They are shown to be functions of the relative ion composition and the ratios of the electron to ion temperatures, and can be described in terms of a 'reduced' Mach number. As a result of these singularities, polar-wind flows are restricted to O+ velocities on the order of 50 m sec−1 near the critical point.