Acceleration of the solar wind by the interplanetary magnetic field

The effect of the azimuthally symmetric (spiral-model) interplanetary magnetic field on radial solar-wind flow is reexamined. It is found that when the azimuthal motion of the plasma due to this field is considered, there is no significant radial acceleration of the plasma by the magnetic field. This result contradicts a recent calculation by Whang, who found a 17 percent increase in solar-wind velocity due to acceleration by the spiral-model magnetic field. This acceleration is an artifact of his model, caused by the neglect of azimuthal motion of the plasma, and is diminished by a factor 10 when azimuthal motions are included. Subject headings: interplanetary medium - plasmas - solar wind