Lower limit of stationary shock strength in adiabatic flows

We show that there is a lower limit of the shock strength Σ=M-/M+, where M- and M+ are the Mach numbers before and after the shock, for adiabatic flows in vertical equilibrium. The limit is independent of the nature of the force field governing the flow or the mass flux and only depends upon the adiabatic index. (author). 3 refs, 2 figs