Intermittent Pulsars

Transient phenomena are usually difficult to find and characterise, particularly if much of the time is spent in a null state. This is true of two recently discovered types of transient radio source, namely the Rotating Radio Transient sources (RRATs) and the Intermittent Pulsars. Both spend much of their time invisible in quite different ways, and both have underlying periodicities which are attributable to rotating magnetic neutron stars. In these circumstances, they also represent the small tips of much larger populations which may cause us to revise our views of what “normal” neutron star behaviour is. RRATS are objects which emit occasional single pulses of radio emission, perhaps once every 100–1,000 rotation periods of the neutron star. The phenomenon is described in detail elsewhere in this volume [9]. The intermittent pulsars on the other hand behave like normal regular pulsars for intervals of time measured in days or years, with longer intervals when there is no emission at all. In this paper, we discuss the phenomenon, the search for other instances, the implications for pulsar magnetospheric physics and the galactic population of such objects.