When the interplanetary magnetic field is northward, wave-particle cross-field transport may contribute to solar wind-magnetosphere coupling. Such transport is studied here through the use of hybrid computer simulations (particle ions, fluid electrons with nonzero mass) carried out in the x-y plane of a plasma with a density gradient in the x direction, no average flow speed, and a magnetic field B=B(x)zˆ. At early times, the lower hybrid drift instability grows on the plasma gradient. However, at times long compared to an ion gyroperiod, the fluctuations coalesce to longer wavelengths in the y-direction and nondiffusive density x-profiles emerge which exhibit ''plateaus'' and ''inclusions'' qualitatively similar to those observed by ISEE near the magnetopause. These results call into question critical assumptions of quasilinear theories of cross-field transport by this instability. ¿ American Geophysical Union 1990