Magnetic Field Evolution in an Accreting White Dwarf

Abstract

I discuss the evolution of the magnetic field of an accreting white dwarf. I show that the ohmic decay time is 7-12 billion years for the lowest order decay mode, almost independent of core temperature or mass. I then show that the magnetic field structure is substantially altered by accretion if the white dwarf mass increases at a rate more than 1-5 x 10^(-10) solar masses per year. I discuss the implications of this result for observed systems, including the possible evolutionary link between AM Hers and intermediate polars.