MHD simulation of accretion processes in magnetic cataclysmic variable EX Hya

Abstract

A hierarchical numerical model for investigation of the accretion processes in the magnetic cataclysmic variable EX Hya has been described. The coarsest level of the hierarchy corresponds to the accretion disk formation due to the mass transfer. The intermediate level describes the structure of the white dwarf magnetosphere. The finest level corresponds to the formation of the accretion curtain at the inner edge of the accretion disk. The model is based on the equations of the modified MHD, where a strong external magnetic field acts as an efficient fluid with which the plasma interacts. Results of simulations show that the accretion in EX Hya proceeds via accretion columns that have curtain-like shapes. These columns are very thin and the accretion regions cover a small fraction of the accretor surface. Numerical results agree with the parameters of the EX Hya system as determined by Semena et al. (2014).