Acceleration of Cosmic Rays at the Solar-Wind Boundary

The acceleration of fast charged particles by outward-moving magnetic irregularities at the solar- wind boundary is examined. If the particle motion beyond the boundary can be described as diffusion with mean free path X, this acceleration is important if X is <0(1 a.u.). On the other hand, if the magnetic field beyond the boundary is smooth enough that X is greater than 1 au., then this acceleration pro- duces a negligible effect. It is concluded that no observational or theoretical arguments preclude X <0 (1 a.u) beyond the solar-wind boundary, particularly for low-energy particles with energies <1 GeV. The possible acceleration of low-energy solar cosmic rays is indicated. Acceleration by the solar wind must be regarded as a potential "local" source of cosmic rays which have passed through zero grams of matter since being accelerated. This effect may help explain recent observations of low-energy "galactic" cosmic rays which suggest more than one source for these particles