  Glitches are sudden spin-up events of pulsars and are usually thought to be
induced by unpinning of neutron superfluid vortices in pulsar crusts. Unpinning
and repinning of superfluid vortices, and even thermoelectric effects induced
by the deposited heat released during glitches, may vary the velocity fields in
pulsars. We show that the generally invoked magnetic dipole fields of pulsars
cannot remain stationary during the variation of the velocity fields, so that
multipole components must be generated. We argue that the increase of the spark
frequency of periodic radio pulses is the indicator for the emergence of the
multipole components. Interpretations of pulsar nulling, rebrightening of
radio-quiet magnetars, differences between Crab and Vela pulsars after
glitches, and extra-galactic fast radio burst-like events from SGR 1935+2154
have been proposed based on the influence of the variation of the velocity
field on the magnetic field.

High Energy Astrophysical Phenomena