Scattering of electromagnetic waves by counter‐rotating vortex streets in plasmas

The scattering of electromagnetic waves from counter‐rotating vortex streets associated with nonlinear convective cells in uniform plasmas has been considered. The vortex street solution of the Navier–Stokes or the Hasegawa–Mima (and of the ‘‘sinh‐Poisson’’) equation is adopted as a scatterer. Assuming arbitrary polarization and profile function for the incident electromagnetic field, a compact expression for the scattering cross section has been obtained. Specific results for the differential cross section are obtained for the case in which the incident beam has a Gaussian profile and propagates as an ordinary mode. The results show that when the characteristic wavelength of the vortex street (λv=2π/a) is larger than that of the incident electromagnetic wave (λi=2π/ki), the differential cross section dσ/dΩ has a very well‐defined angular periodicity; in fact, it is a collection of Gaussians varying as exp[−f(kiw)2], where w is the waist and f is a function expressing a kind of ‘‘Bragg condition.’’ On the...