Inter-relationship between the Two Emission Cones of B1237+25
  The origin of two distinct pairs of conal emission components in pulsars,
associated with the "outer" and the "inner" emission cones, as well as the
marked difference in their observed spectral properties, is poorly understood.
The sub-pulse modulation in the corresponding conal components, if mapped back
to the underlying system of sub-beams rotating around the magnetic axis in the
polar cap, as envisioned by Ruderman & Sutherland (1975), provides a potential
way to investigate the emission morphologies in the two conal regions, and more
importantly, any inter-relationship between them. The bright pulsar B1237+25
with its special viewing geometry where the sightline traverses almost through
the magnetic axis, along with a rich variety in pulse-to-pulse fluctuations,
provides an excellent, but challenging opportunity to map the underlying
emission patterns across the full transverse slice of its polar emission
region. We present here our analysis on a number of pulse-sequences from this
star to map and study any relationship between the underlying patterns
responsible for emission in the two pairs of presumed conal-components and a
core-component of this pulsar. The results from our correlation analysis of the
two conal emission patterns strongly support the view that the two cones of
this pulsar (the outer and the inner cone) originate from a common system of
sub-beams. We also see evidence for a twist in the emission columns, most
likely associated with a corresponding twist in the magnetic field structure.
We discuss these results, and their implications, including a possibility that
the core component of this pulsar shares its origin partly with the conal
counterparts.
