The SKA will be transformational for many areas of science, but in particular for the study of neutron stars and their usage as tools for fundamental physics in the form of radio pulsars. Since the last science case for the SKA, numerous and unexpect
ed advances have been made broadening the science goals even further. With the design of SKA Phase 1 being finalised, it is time to confront the new knowledge in this field, with the prospects promised by this exciting new telescope. While technically challenging, we can build our expectations on recent discoveries and technical developments that have reinforced our previous science goals.
Pulsars are famed for their rotational clock-like stability and their highly-repeatable pulse shapes. However, it has long been known that there are unexplained deviations (often termed timing noise) from the rate at which we predict these clocks sho
uld run. We show that timing behaviour often results from typically two different spin-down rates. Pulsars switch abruptly between these states, often quasi-periodically, leading to the observed spin-down patterns. We show that for six pulsars the timing noise is correlated with changes in the pulse shape. Many pulsar phenomena including mode-changing, nulling, intermittency, pulse shape variability and timing noise are therefore linked and caused by changes in the pulsars magnetosphere. We consider the possibility that high-precision monitoring of pulse profiles could lead to the formation of highly-stable pulsar clocks.
High time resolution observations of PSR B0906-49 (or PSR J0908-4913) over a wide range of frequencies have enabled us to determine the geometry and beam shape of the pulsar. We have used the position angle traverse to determine highly-constrained so
lutions to the rotating vector model which show conclusively that PSR B0906-49 is an orthogonal rotator. The accuracy obtained in measuring the geometry is unprecedented. This may allow tests of high-energy emission models, should the pulsar be detected with GLAST. Although the impact parameter, beta, appears to be frequency dependent, we have shown that this is due to the effect of interstellar scattering. As a result, this pulsar provides some of the strongest evidence yet that the position angle swing is indeed related to a geometrical origin, at least for non-recycled pulsars. We show that the beam structures of the main pulse and interpulse in PSR B0906-49 are remarkably similar. The emission comes from a height of ~230 km and is consistent with originating in a patchy cone located about half way to the last open field lines. The rotation axis and direction of motion of the pulsar appear to be aligned.
The behaviour of the pulsar spectrum at high radio frequencies can provide decisive information about the nature of the radio emission mechanism. We report recent observations of a selected sample of pulsars at lambda=9mm (32 GHz) with the 100-m Effe
lsberg radio telescope.Three pulsars, PSR B0144+59, PSR B0823+26, and PSR B2022+50, were detected for the first time at this frequency. We confirm the earlier flux density measurements for a sample of six pulsars, and we are able to place upper flux density limits for another 12 pulsars. We find that all pulsar spectra have a simple form that can be described using only three parameters, one of which is the lifetime of short nano-pulses in the emission region.The study of the transition region from coherent to incoherent emission needs further and more sensitive observations at even higher radio frequencies.
