The number density, the particle flux, the momentum fluxes, and the energy flux are calculated in a model ion exosphere with an open magnetic field, for an asymmetric Maxwellian velocity distribution (i.e., ∼exp[-β(v-u) 2]). Numerical calculations for the polar ionosphere of the earth show that this asymmetry does not qualitatively affect the results obtained with a symmetric velocity distribution function (u = 0), i.e., the protons are accelerated outward and escape with a supersonic flow speed.