Parallel electric fields in nonlinear magnetosonic waves

The electric field parallel to the magnetic field, E-parallel to, in nonlinear magnetosonic waves is studied theoretically and numerically. In the calculation of E-parallel to based on the conventional reductive perturbation method, the terms related to the magnetic pressure cancel, and E-parallel to is proportional to the electron temperature T-e. With a modified perturbation scheme assuming that the wave amplitude is in the range (m(e)/m(i))(1/2)<epsilon < 1, an expression for E-parallel to is obtained that is proportional to the magnetic pressure in a cold plasma. Its integral along the magnetic field, F=-integral E(parallel to)ds, is proportional to epsilon(2)m(i)v(A)(2). One-dimensional, fully kinetic, electromagnetic particle simulations verify the theoretical predictions for small-amplitude waves. Further, they demonstrate that eF becomes of the order of epsilon(m(i)v(A)(2)+Gamma T-e(e)) in large-amplitude [epsilon similar to O(1)] oblique shock waves. These theory and simulations indicate that E-parallel to in magnetosonic waves can be strong in a strong magnetic field. (C) 2007 American Institute of Physics.