  Observations obtained in the last years challenged the widespread notion that
rotation-powered neutron stars are steady X-ray emitters. Besides a few
allegedly rotation-powered neutron stars that showed "magnetar-like"
variability, a particularly interesting case is that of PSR B0943+10. Recent
observations have shown that this pulsar, well studied in the radio band where
it alternates between a bright and a quiescent mode, displays significant X-ray
variations, anticorrelated in flux with the radio emission. The study of such
synchronous radio/X-ray mode switching opens a new window to investigate the
processes responsible for the pulsar radio and high-energy emission. Here we
review the main X-ray properties of PSR B0943+10 derived from recent
coordinated X-ray and radio observations.
