It is believed that an isolated pulsar loses its rotational energy mainly through a relativistic wind consisting of electrons , positrons and possibly Poynting flux [ 2 , 3 , 4 ] .
As it expands , this wind may eventually be terminated by a shock , where particles can be accelerated to energies of X-ray synchrotron emission , and a pulsar wind nebula ( PWN ) is usually detectable surrounding a young energetic pulsar [ 2 , 3 , 4 ] .
However , the nature and/or energetics of these physical processes remain very uncertain , largely because they typically can not be studied in a time-resolved fashion .
Here we show that the X-ray PWN around the young pulsar PSR B0540–69 brightens gradually up to 32 \pm 8 \% over the mean previous flux , after a sudden spin-down rate ( \dot { \nu } ) transition ( SRT ) by \sim 36 \% in December 2011 , which has very different properties from a traditional pulsar glitch [ 5 ] .
No evidence is seen for any change in the pulsed X-ray emission .
We conclude that the SRT results from a sudden change in the pulsar magnetosphere that increases the pulsar wind power and hence the PWN X-ray emission .
The X-ray light curve of the PWN suggests a mean life time of the particles of 397 \pm 374 days , corresponding to a magnetic field strength of 0.78 _ { -0.28 } ^ { +4.50 } mG in the PWN .