as a function of atmospheric gas pressure p_gas for the same substellar atmosphere as in Fig. 1. is plotted for electron temperatures T_e = T_gas ( K), green), 1 eV (≈ 10⁴, blue), 10 eV (≈ 10⁵, red) and 100 eV (≈ 10⁶, magenta). The plot also shows calculated using Bohm (dash) and OML (solid) theory to obtain the floating potential φ_f. The mean grain size ⟨ a ⟩ as a function of gas pressure p_gas for the example substellar atmosphere considered here is over plotted (black).