Propeller effect during magnetocentrifugal plasma acceleration

We study the effect of magnetic-field axial asymmetry on the magnetocentrifugal acceleration of plasma when it flows in a source’s rotating magnetosphere (propeller effect). For an axisymmetric steady plasma flow, the first corrections to the energy that arise when the source rotates slowly are proportional to Ω⁴, suggesting a highly inefficient plasma acceleration. Magnetic-field axial asymmetry is shown to substantially modify the acceleration. The first corrections arise even in the first order in Ω. The plasma acceleration turns out to be considerably more efficient in a nonaxisymmetric magnetic field.