Collisionless solar wind in the spiral magnetic field

The two-fluid model for the solar wind of Hollweg (1970) is reconsidered with the inclusion of the spiral structure of the interplanetary magnetic field. In the present model, the protons are assumed to become collisionless beyond 0.1 AU from the sun, whereas the electrons are treated hydrodynamically and the electron temperature is supposed to obey the polytropic law. The electric field established from the charge separation, which is assumed to be derivable from a potential, tends to enhance the velocity of the solar wind at 1 AU to a value over 300 km/sec. The proton thermal anisotrophy T∥/T⊥ at the orbit of the earth is reduced from the value of 50 in the model with the radial magnetic field to the value of 11 in the present model.