Unidirectional modes induced by nontraditional Coriolis force in stratified fluids

By using tools from topology, we unveil the existence of new undirectional modes supported by compressible rotating stratified flows. We relate the emergence of those modes to the concomitant breaking of time-reversal symmetry by Coriolis force and vertical mirror symmetry by density stratification and gravity. In contrast with previous unidirectional surface waves induced by a field perpendicular to the flow, we highlight the unexpected role played by the nontraditional part of the Coriolis force which is induced by a rotation field tangent to the surface. Those modes are trapped along interfaces separating regions with different stratification properties, and we show that one is a generalized atmospheric Lamb wave whose direction of propagation is selected by nontraditional Coriolis effects.