In 2004, McLaughlin et al. discovered a phenomenon in the radio emission of PSR J0737-3039B (B) that resembles drifting sub-pulses. The repeat rate of the sub-pulses is equal to the spin frequency of PSR J0737-3039A (A); this led to the suggestion that they are caused by incidence upon Bs magnetosphere of electromagnetic radiation from A. Here we describe a geometrical model which predicts the delay of Bs sub-pulses relative to As radio pulses. We show that measuring these delays is equivalent to tracking As rotation from the point of view of an hypothetical observer located near B. This has three main astrophysical applications: (a) to determine the sense of rotation of A relative to its orbital plane; (b) to estimate where in Bs magnetosphere the radio sub-pulses are modulated and (c) to provide an independent estimate of the mass ratio of A and B. The latter might improve existing tests of gravitational theories using this system.
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