Switched magnetospheric regulation of pulsar spin-down
  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 should 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 pulsar's magnetosphere. We consider the
possibility that high-precision monitoring of pulse profiles could lead to the
formation of highly-stable pulsar clocks.
