Published online by Cambridge University Press: 01 February 2007
We consider the nonlinear interactions between upper-hybrid (UH) and Alfvén modes in a magnetized electron–ion plasma containing a fraction of stationary charged dust grains. The interaction is governed by a pair of equations for the UH wave envelope including the relativistic electron mass increase and the density and compressional magnetic field fluctuations associated with the Alfvén modes that are, in turn, driven by the ponderomotive force of the UH waves. The coupled mode equations are then Fourier analyzed to obtain a new dispersion relation, which admits new classes of modulational instabilities. The existence of a cusp-shaped UH envelope soliton is also predicted. The result can have relevance to the electron acceleration by sharply localized UH waves in the dusty magnetosphere of Saturn.