Comparison of distribution functions: the n-function with n = 3 is indicated by the blue line, the distribution function of reflected electrons (ΔΦ = 0) by the red line, the seed (Maxwellian) distribution function for reflected electrons by the green line, and the total upstream distribution, i.e. the sum of the reflected electrons and the seed particles, by the black line. The blue and red lines are identical to the ones in Fig. 1.