Strongly nonlinear magnetosonic waves and ion acceleration

The electromagnetic fields associated with a nonlinear compressional Alfven wave propagating perpendicular to an arbitrarily strong external magnetic field are derived. While recovering the known properties of nonlinear Alfven waves in the weakly magnetized regime, new scaling laws are found for the strongly magnetized case. It is shown that the electric field increases only with the first power of the external magnetic field strength for the strongly magnetized and high phase velocity case relevant for ion acceleration to high energies. An experimental setup suitable for the pickup and acceleration of background plasma ions that is not subjected to detrapping of ions due to a vxB acceleration is sketched. (C) 1998 American Institute of Physics. [S1070-664X(98)03010-9].