Interaction between nulls and emission in the pulsar B0834+06

We present a detailed study of the single pulses of the bright radio pulsar B0834+06, and offer evidence that the dominant periodic modulation in this pulsar's emission governs the occurrence of nulls. The nulls of B0834+06 constitute approximately 9 per cent of the total pulses and we demonstrate that they do not occur at random in the pulse sequence. On the contrary, they are found to occur preferentially close to the minimum of the pulsar's emission cycle, whose period jitters around a central value of P ₃≈ 2.17 rotation periods. It is likely that the intrinsic duration of the nulls averages about 0.2 times the pulsar rotation period. Surprisingly, the clearly distinct population of nulls and partial nulls of B0834+06 exhibit a two-peak profile slightly broader than that of the normal emission. This is in contrast to the profile of extremely weak normal pulses, which is narrower than the overall profile. A flow/counterflow model for the pulsar's two components can reproduce the essential observed features of the emission in its dominant mode, with nulls occurring at the point where the minima of the two systems are aligned. This suggests that the observed nulling rate is determined by the chance positioning of our sightline with respect to the system. If the flow is interpreted as part of a circulating carousel, a fit yields a best estimate of 14 'sparks'.