The particle and energy balance equations in the scrape-off layer (SOL) plasma are solved analytically in a rectangular domain. The parallel flow is supposed to be convective, whereas the cross field flow is assumed diffusive, with modifications due to a radial E field. When the energy balance equation is neglected we get a quadratic equation for h, the e-folding density scale length. The normalized e-folding scale length Ahlo (Ao = h for E = 0) is a function of single parameter a (= e E V k T . where T is the plasma temperature, e the elementary charge and k is Boltzmann's constant), and monotonically increases with a. Taking the energy balance equation into account and neglecting R, (the ionization rate), the quadratic equation is further simplified. and Ahlo again depends on a single parameter, determined by Q (the input power flux), D (the cross field diffusion coefficient), y (the sheath transmission coefficient for energy) and n, , (the plate density). Now Ahlo decreases with Q and increases linearly with D. y and np. The variation of A & , with E is estimated for TdeV and ITER. We find that, by a proper choice of parameters, biasing may be a very valuable tool to modify the SOL properties at modest E fields, provided the heat load on the divertor plate is not excessively large.