On the 'flip-flop' instability of Bondi-Hoyle accretion flows

Using a highly simplified analytic treatment of the shock cone obtained in Bondi-Hoyle accretion flows past a compact object and the results of stability analyses of the accretion line, we demonstrate that the 'flip-flop' instability discovered recently in numerical calculations, in which the wake oscillates from side to side, has a relatively simple physical interpretation. The results of our analysis are in agreement with those obtained in multidimensional numerical hydrodynamic calculations.