Shock formation in accretion columns - a 2D radiative MHD approach

We investigate the effects of radiation and magnetic fields on the formatio n, structure, and stability of the axisymmetric shock and settling flow pro duced by accreting gas initially directed towards a non rotating stellar su rface from a polar column with fret-fall speed. We perform one dimensional reference calculations as well as two dimensiona l calculations with zero, weak and strong magnetic fields. In the one dimen sional case and weak magnetic field case in two dimensions, we verify the e xistence of the cooling over-stability for low accretion rates, finding tha t the flow is stabilized if the accretion rate exceeds 5 x 10(16) gr s(-1) onto a solar mass white dwarf of radius 10(9) cm. In the two dimensional cases with weak magnetic field (beta = magnetic pres sure/gas pressure = 0.1) a strong pressure driven latitudinal flow also occ urs causing gas to move towards the equator. This strong latitudinal motion is suppressed and the amplitude of short per iod oscillations considerably reduced in cases we consider in which the mag netic field (hereafter MF) is strong enough (beta = 10) to confine the flow to the polar column. This suggests that further investigations are needed in order to understand the short period oscillations in accreting stars wit h a strong MF.