  The partially screened vacuum gap model (PSG) for the inner acceleration
region in normal radio pulsars, a variant of the pure vacuum gap model,
attempts to account for the observed thermal X-ray emission from polar caps and
the subpulse drifting timescales. We have used this model to explain the
presence of death lines, and extreme location of PSR J2144$-$3933 in the
$P-\dot{P}$ diagram. This model requires maintaining the polar cap near a
critical temperature and the presence of non-dipolar surface magnetic field to
form the inner acceleration region. In the PSG model, thermostatic regulation
is achieved by sparking discharges which are a feature of all vacuum gap
models. We demonstrate that non-dipolar surface magnetic field reduces polar
cap area in PSR J2144$-$3933 such that only one spark can be produced and is
sufficient to sustain the critical temperature. This pulsar has a single
component profile over a wide frequency range. Single-pulse polarimetric
observations and the rotating vector model confirm that the observer's
line-of-sight traverses the emission beam centrally. These observations are
consistent with a single spark operating within framework of the PSG model
leading to single-component emission. Additionally, single-pulse modulations of
this pulsar, including lack of subpulse drifting, presence of single-period
nulls and microstructure, are compatible with a single spark either in PSG or
in general vacuum gap models.
