Parkes observations for project P873 semester 2014APRS

The radio emission process in pulsars is not understood. However, pulsar timing is successfully used in extracting exciting science from radio pulsars and their environments. We are now approaching the point where the limits in our understanding of pulsar emission, affect the precision of pulsar timing experiments. State-switching and intermittent pulsars both show correlated changes between the shape of the average pulse profile and the spin-down rate, that is the first derivative of the rotational period. The spin-down rate changes have been shown to be related to changes in the torque imparted on the neutron star by magnetospheric currents. Our team have recently uncovered an extreme example of a state-switching pulsar in J0738-4042, adding to the small sample of known such sources, and showing that variability exists on a wide range of timescales. We now propose a further experiment to understand the connection between emission changes and timing irregularities. For this, we will target pulsars with well-known emission variability, which occurs on timescales of the order of the pulsar period, so-called moding and nulling. Using weekly monitoring, we will show whether there is a connection between the well known short timescale phenomena, and the long term intermittency and state-switching. Our ultimate objective is to understand what causes long-term variability in pulsars, be it an internal or external cause, and to include this knowledge in improved pulsar timing models.