  We use fluctuating hydrodynamics to evaluate the enhancement of thermally
excited fluctuations in laminar fluid flow using plane Couette flow as a
representative example. In a previous publication [J. Stat. Phys. vol. 144
(2011) p. 774] we derived the energy amplification arising from thermally
excited wall-normal fluctuations by solving a fluctuating Orr-Sommerfeld
equation. In the present paper we derive the energy amplification arising from
wall-normal vorticity fluctuation by solving a fluctuating Squire equation. The
thermally excited wall-normal vorticity fluctuations turn out to yield the
dominant contribution to the energy amplification. In addition, we show that
thermally excited streaks, even in the absence of any externally imposed
perturbations, are present in laminar fluid flow.
