Parallel electric fields in nonlinear magnetosonic waves in an electron-positron-ion plasma

The electric field E-parallel to along the magnetic field B in nonlinear magnetosonic waves in a three-component plasma is studied with theory based on a three-fluid model and with fully kinetic, electromagnetic, particle simulations. The theory for small-amplitude (epsilon << 1) pulses shows that the integral of E-parallel to along B, F=-integral E(parallel to)ds, is proportional to epsilon(p(e0)-p(p0)) in warm plasmas, where p(e0) and p(p0) are, respectively, the electron and positron pressures, and proportional to epsilon(2)m(i)upsilon(2)(A)/(1+upsilon(2)(A)/c(2))(3) in cold plasmas, where upsilon(A) is the Alfven speed. These predictions are verified with simulations. Furthermore, for shock waves with epsilon similar to O(1), simulation values are consistent with the phenomenological relation n(e0)eF similar to is an element of(rho nu(2)(A)+Gamma(e)p(e0))(n(i0)/n(e0)), where rho is the mass density and Gamma(e) is the specific heat ratio. These results indicate that Ell can be strong in strong magnetic fields. (C) 2008 American Institute of Physics.