Reaction fronts in an ionic autocatalytic system with an applied electric field

The effects of applying an electric field to an ionic autocatalytic reactio n with a cubic rate law are discussed. The constant field strength approxim ation is made and the resulting equations for the model examined by first c onsidering the corresponding travelling wave equations. These show ranges o f field strength over which travelling waves do not exist, these ranges bei ng dependent on whether D>1 or D<1, where D is the ratio of diffusion coeff icients of autocatalyst and substrate. Numerical simulations of the full sy stem are obtained and these show that, when travelling waves exist, these a re formed as the long time behaviour of the system. When travelling waves d o not exist, complete electrophoretic separation of the reacting ionic spec ies results, forming separate fronts in autocatalyst and substrate, their d irection of propagation depending on D. Comparisons with a related problem with a quadratic rate law are made and the implications for experiments bas ed on the iodate-arsenous acid reaction assessed.