  Pulsar electrodynamics could be relevant to the physics of stellar surface,
which remains poorly understood for more than half a centenary and is difficult
to probe due to the absence of direct and clear observational evidence.
Nevertheless, highly-sensitive telescopes (e.g., China's Five-hundred-meter
Aperture Spherical radio Telescope, FAST) may play an essential role in solving
the problem since the predicted surface condition would have quite different
characteristics in some models of pulsar structure, especially after the
establishment of the standard model of particle physics. For instance, small
hills (or ``zit'') may exist on solid strangeon star surface with rigidity,
preferential discharge, i.e., gap sparking, may occur around the hills in the
polar cap region. In this work, with the 110-min polarization observation of
PSR B0950+08 targeted by FAST, we report that the gap sparking is significantly
non-symmetrical to the meridian plane on which the rotational and magnetic axes
lie. It is then speculated that this asymmetry could be the result of
preferential sparking around zits which might rise randomly on pulsar surface.
Some polarization features of both single pulses and the mean pulse, as well as
the cross-correlation function of different emission regions, have also been
presented.
