  It is found that in magnetized electrostatic plasma flows the velocity shear
couples ion-acoustic waves with ion-cyclotron waves and leads, under favorable
conditions, to their efficient reciprocal transformations. It is shown that in
a two-dimensional setup this coupling has a remarkable feature: it is governed
by equations that are exactly similar to the ones describing coupling of sound
waves with internal gravity waves [Rogava & Mahajan: Phys. Rev. E vol.55, 1185
(1997)] in neutral fluid flows. Using another noteworthy quantum mechanical
analogy we calculate transformation coefficients and give fully analytic,
quantitative description of the coupling efficiency for flows with low shearing
rates.
