Diffusion of electrons in time-dependent E(t) x B(t) fields

We present results of Monte Carlo simulations for the components of electro n diffusion tensor in time-varying E x B fields. In particular we follow th e development of anomalous behaviour due to the change of the sign of the e lectric field which was found for longitudinal diffusion in purely electric rf fields (K Maeda et al 1997 Phys. Rev. E 55 5901). Similar behaviour was found to be present in crossed fields for the longitudinal NDE component a nd absent for one perpendicular NDB component. It turns out that anomalous behaviour for the NDE x B component is induced even for a relatively small magnetic field. Reid's ramp model was used for calculations but the conclus ions are quite general as these effects occur for most real gases. The tran sient kinetic phenomena are usually not taken into account in continuum mod els of rf plasmas. Our results show that it is important to include such pr ocesses in modelling and to verify the electron kinetic codes for their abi lity to represent the transient phenomena.