We have performed fully-kinetic simulations of X-B and O-X-B mode conversion in one and two dimensional setups using the PIC code EPOCH. We have recovered the linear dispersion relation for electron Bernstein waves by employing relatively low amplitu
de incoming waves. The setups presented here can be used to study non-linear regimes of X-B and O-X-B mode conversion.
It is shown that electrons with momenta exceeding the `free electron limit of $m_eca_0^2/2$ can be produced when a laser pulse and a longitudinal electric field interact with an electron via a non-wakefield mechanism. The mechanism consists of two st
ages: the reduction of the electron dephasing rate $gamma-p_x/m_ec$ by an accelerating region of electric field and electron acceleration by the laser via the Lorentz force. This mechanism can, in principle, produce electrons that have longtudinal momenta that is a significant multiple of $m_eca_0^2/2$. 2D PIC simulations of a relatively simple laser-plasma interaction indicate that the generation of super-ponderomotive electrons is strongly affected by this `anti-dephasing mechanism.
