Abstract
In this work, we expand on a comment by Lyne et al. (2017), that intermittent pulsars tend to congregate near a stripe in the logarithmic period versus period-derivative diagram. Such a stripe represents a small range of polar cap electric potential. Taking into account also the fact (already apparent in their Figure 7, but not explicitly stated there) that high-fraction nulling pulsars also tend to reside within this and an additional stripe, we make the observation that the two stripes further match the “death lines” for double- and single-pole interpulses, associated with nearly orthogonal and aligned rotators, respectively. These extreme inclinations are known to suffer from pair production deficiencies, so we propose to explain intermittency and high-fraction nulling by reinvigorating some older quiescent (no pulsar wind or radio emission) “electrosphere” solutions. Specifically, as the polar potential drops below the two threshold bands (i.e., the two stripes), corresponding to the aligned and orthogonal rotators, their respective magnetospheres transition from being of the active pair-production-sustained-type into becoming the electrospheres, in which charges are only lifted from the star. The borderline cases sitting in the gap outside of the stable regime of either case manifest as high-fraction nullers. Hall evolution of the magnetic field inside orthogonally rotating neutron stars can furthermore drive secular regime changes, resulting in intermittent pulsars.
Highlights
Neto, Hermano Velten and GustavoSome pulsars show systematic long term variations in their emission behaviors, in the form of intermittency [1,2,3,4], whereby the emission ceases for a significant period of time before turning back on again
It is noted by [4] that such lines/stripes are likely significant because they correspond to constant potential drops across polar caps, in the rudimentary vacuum dipole model of the pulsar magnetosphere, which serves as a baseline parameter for constructing more sophisticated models
We propose that chargeabundant active magnetospheres and charge-starved quiescent electrospheres describe the live and dead pulsars that are separated by the
Summary
Some pulsars show systematic long term variations in their emission behaviors, in the form of intermittency [1,2,3,4], whereby the emission ceases for a significant period of time before turning back on again. It is noted by [4] that such lines/stripes are likely significant because they correspond to constant potential drops across polar caps (abbreviated as P below), in the rudimentary vacuum dipole model of the pulsar magnetosphere (summarized in Appendix A.1), which serves as a baseline parameter for constructing more sophisticated models (summarized in Appendixes A.2 and A.3). Zooming further out to encompass all pulsars, it is noteworthy that not all pulsars near the proposed lines share such variability, so the variable population must correspond to special configurations possessing particular but not abnormal (otherwise the pulsars likely will not behave normally in their “on” states) parameters Recalling that those lines of constant P are meaningful only when comparing pulsars of similar.
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